What are some ways you can build credibility with Sales, ensuring that they will leverage your messaging and materials?

Well, it’s difficult to “ensure” that anyone is going to use any set of materials. I would look at it from the point of view where PMM's job is to create messaging and materials that sales would want to use. 

Understand/Build your Voice of the Customer 

To build initial credibility, it’s essential to champion the voice of the customer. You need to make sure you understand the buyer as well as they do, or your credibility will never get off the ground. Understanding the voice of the customer also means that you're empathetic to what’s going on with your buyer. When you visibly demonstrate this, you can start on a solid baseline when working with sales. 

Involve Sales in the Process 

Again, get out of the ivory tower. As you develop core materials, involve them in the process. Heck, they might have some great suggestions, nuggets and insights that may be useful. Do this with good reps that have demonstrated previous success and have a “repeatable style” where lessons can be translated to other reps. 

Share Usable Insights 

Sales loves easy to understand insights and anecdotes that they can pull out of a hat. As part of your work stream, build a library or inventory of these where you can use them in messaging and materials. Example: User stories, customer/buyer stories, case studies, data points, etc. 

Man, I love this question! As PMMs so much of our work only has impact if it has engagement from others, and the only way to get that engagement is by having credibility in the organization.

This won't be a perfect list or exhaustive, but some things that come to mind are:

• Take the time to understand their world: Get out in the field with them, get to know them over drinks, learn what customers are saying about how the product is/isn't meeting their needs, see how our assets do in the wild, etc. There's so many steps we can take to demonstrate we care, that we recognize that it's hard, that we empathize with what it takes to chip away at their quota. If we don't understand their world, we risk coming across as tone deaf which will immediately crater trust and credibility.
• Seek out their opinion and listen to them: Given where we sit in the organization and the amount of visibility and strategic insight we have across the business and the market, it's easy to fall into the trap of thinking we know the answer of what will work and why. It's important to remember, though, that there's so much that happens on the front line that we just aren't the experts on: our sales, client success, and support teams are the masters there. Demonstrate that you recognize they know more than you in certain areas and you value their opinion. Bring them into your process when you're developing pitches, playbooks, collateral, messaging, whatever it may be. Engage them as advocates for the work you're trying to land in the field or in the organization. 
• Be selfless: Try and maintain a mindset of "my job is about making other people successful." It can be tempting to get caught up in trying to drive a certain impact or agenda and lose sight of how the best impact we can make is when we uplevel the strategic decision-making and in-market execution of the entire organization. When you are really trying hard to engage with people from a place of "how can I help make you and your team successful," people can interpersonally pick up on that and it makes a big difference for earning credibility.
• Do high quality work: Be a fantastic project manager (provide lots of visibility and opportunity for others to shar einput at the appropriate times; manage toward timelines; etc.) and hold yourself to a very high standard for your deliverables. 
• Learn to say no: As a PMM you need to be ruthless in how you prioritize your work. There simply aren't enough PMMs or time under the sun to do all of the things that might be worth doing. Make sure you're focusing on doing a few of the most important things extremely well; avoid at all costs feeling like you have to execute on every ask that comes your way.

Credibility is about playing the long-game. Your reputation takes time to build and it won't happen overnight. And you can't take your eye off the ball when you've earned hard won credibility because at the end of the day this is about relationships and consistency is key.

The best sales reps I’ve seen rely on people and resources across the company to win deals, but these same reps are also very particular about the materials they use and the people they invite to meetings. This attention to detail in the customer experience is what drives their success.

The million dollar question to ask yourself is: “How can I be a value-add? What can I provide that they can’t get from anyone else at the company?”

If you aren’t sure, just ask them what they need that would make their job easier. It might be a custom sales deck for a big meeting, a new two-pager, or some highly-specific competitive intelligence. Once you deliver for them a couple of times, they’ll trust you and turn to you more. You’ll know you’re there when you get asked for advice on positioning in big deals, or even get invited to meetings to talk to customers directly.

A good place to start is with newer or more junior reps. They’re most likely to welcome help from anywhere they can get it, and once you help someone win a deal, word gets out quickly. That cements the relationship, at which point you can ask for their help in testing your materials and providing feedback.

This is all about relationships, credibility/expertise, and your ability to help sellers. Once you can demonstrate that you can help them by bringing your perspective to what they're doing to make them smarter, more consultative, more well-informed, etc., the more they'll trust you and the better your end product - in this case - messaging - will be. Get curious about what deals are giving sellers trouble, and where in the sales process they're getting stuck. Ask them if you can learn more. Shadow their calls. Read and learn as much as you can about the category and the market to give you a deep understanding of the buyer's pain points and challenges so that you can provide that higher altitude perspective. If you do this well, sellers may start asking you to join calls to provide that perspective as a subject matter expert. And as you create materials for sales, don't do it in a vacuum. Socialize it broadly with a cross-section of sellers to get their input and refine the material. 

I am going to answer this question as a former sales person plus as someone who produces content and train sales on new messaging. Sales people will listen to you if (1) they feel that you can help them close deals (2) you understand their painpoints as a sales person. So two things that I have done, which makes my training effective. (1) I make it a point to join calls as a silent listener, and when I train a team on some new messaging, I would reference the call that i attended as an example on how / why new messaging might be more effective on said call. A complimentary approach to being on calls is to leverage and befriend a top sales person and work with them on the new messaging. Have this person to test new messaging and work with them till they are successful. Then leverage them in training because reps will follow the rep that closes the most deals. 

These are all great answers. To add just a little bit to Gaurav's helpful points of consistency and ease...

Consistency--keep content updated with market and competitor movements. Did a competitor change pricing? Launch a new product? Change the messaging on their product pages? If you're tracking this stuff consistently AND you keep your sales collateral updated with those insights (battlecards, competitive profiles, etc.) sales will continue to leverage your materials because they know that it is accurate and you're on top of it, thus building your credibility.

Ease--agreed that you should centralize as much as possible. I think the key is--if you can--try to store materials where your sales team lives, usually your CRM. Lots of tools out there offer integrations with SFDC, other CRMs, etc. One less tool/platform to introduce to your sales team, the better--at least in my experience. 

Great question - great answers. Dave Kong started us with a super framework. As you know, this is not a trivial issue so I would like to add a POV to these answers. (Full disclosure: I am sharing what I have seen as head of a B2B buyer strategy firm. I am so passionate about this, we created an offering to do this called PlaybooksPlus). 

The Key to Sales Thinking

In my experience, sales people are ruthlessly practical - they use what works. So the conversation with them must be ruthlessly focused on 'we know this works'. There is only one way to ensure this -- know in advance what your buyers want. 

What You Need to Know

The way I have seen this work is by knowing things about 'their' buyers they don't know. This might seem impossible but there are some insights that sales cannot know, like why they lose deals, why buyers go dark, and even the real reasons they decide to buy. I believe this comes from doing independent (win/loss) research about the purchase path on deals that went well, went south, and went away (no decision). This can be done well without huge investments of time or budget. 

What You Need to Do

But just knowing this will not change sales outcomes. I believe this insight needs to be handed off from marketing to sales in a framework (a sales playbook) with these characteristics: 

1. Buyer-driven: Your content is vetted by your real buyers to address their real concerns in their language
2. Sales-connected: Your content is tuned with input and buy-in from your most successful sales leaders
3. Scenario-targeted: Your content is written for and delivered to your sales team (say, on their Salesforce dashboard) for the specific need state, ICP, and persona they are addressing at that moment 

I look forward to seeing more candid input on this topic. 

In addition to David's answer, I will also add the following points that should help build the credibility. 

Consistency

You want to continue to deliver fresh content consistently. Consistent doesn't mean high quantity. But you need to follow a consistent cadence. Too many times, marketing will create content in these bursts and then stay back and watch. If your company is selling, then there is always an opportunity to gather insights and share them with your sales team to help them with their selling. 

Make it easy

You need to make it easy for sales team to get access to this information. At the very least, it should be in a central space or centrally accessible. You do not want to give content silos. They will not engage and eventually the engagement will die down. However, it is quite difficult to create a central content portal for sales. It needs a disciplined process and the right tools. 

Use Insights Constructively

Today, several tools offer engagement insights so that you know who is using the content and who isn't. When you see lack of engagement, make sure you approach it in a constructive fashion. Instead of reporting on lack of engagement, ask the reps why are they not engaging with the content. These insights from sales will help you up your content game and also build credibility with sales.  

Meet them where their difficulties are. What, in their minds, is preventing them from closing more, bigger, faster? Maybe you know that messaging is the issue, but until you actually sit with salespeople and understand where they feel their own gaps are, you won't be able to translate that messaging into a format they will be able to use. For example, I've stopped making "buyer personas" the final deliverable. It should always be "business cases" that tell the actual story of how different stakeholders will achieve success with the product.