Do you have a methodology for validating messaging with users before a campaign goes live? I'm thinking of marketing campaigns here, not product or UX.

We do - but we are also iterating here as we speak! In the past, I have reached out to some customers and folks I know in the industry to sit down and do some quick validation on messaing. For example, when we launched our new website and put up our first billboards, we had a good sense of what we wanted to say but wanted to confirm that the direction we were going would resonate. So we schedulded some quick meetings and got raw feedback on some key phrases. We've done the same with changes to our pricing page.

Now this is of course manual and only with a few folks so it isn't validation at scale. That is what we are looking to move to next. We are currently creating a process that will have us partner with Demand Gen to run paid ads testing out some of our messaging around big products and campaigns earlier on in our development process. We are hopeful that will give us more direction too!

Painted door tests are your friend here (google it). You could create two or three landing pages with different message variants, each of which leads to a "request access" form. Depending on what your campaign is for, your message testing could be as simple as running it by product managers or account managers. Or you could grab a few web visitors through a Qualaroo survey and interview them. You could grab people and buy them a coffee at a conference. Basically, there's no big trick to this - you just have to do it. If you're getting feedback on your messaging from your target audience or someone who can reliably act as a proxy for your target audience, you're probably doing it right. 

One thing I've seen past success with is testing out a message with a small subset of users and adjusting prior to blasting your entire database. Same could be done for emails, ads, landing pages, etc.

For a quick example of email: send an a/b test email to 300 people. See the results, then depending on what you find 'wins' continuing that message to the broader group of 10,000.

For websites it is rather easy to use the free version of Optimizely for this to show 10% of your traffic one thing vs the remaining 90% (depending on how much traffic you get to make it statistically relevant).

If it's more for your overall messaging and positioning then I really like Tamara Mendelsohn from Eventbrite's approach. It goes at it in a pretty pragmatic way across surveys and digital channels - https://blog.kissmetrics.com/how-eventbrite-built-scaled-their-marketing/

A few things that I've tried out that have been helpful depending on your time / budget: 

1) Survey to your user base (or prospects) allowing them to choose the homepage (or ad / whatever visual) with their favorite message. Have up to 5 and let them rank them. Then ask what they liked about the message. Super easy / scrappy. Just make sure each has the same visual so you're not confounding the results. 

2) AdWords - Put ads in an ad group on "rotate" (instead of optimize) which helps you get close to an A/B test 

3) Classic email headline A/B test - see which ones get the best open rates.

Hope that helps!