I have a few lenses that I look through for competitive differentiation:
1. The Positioning Canvas -- I mentioned this in an earlier question, but it's worth repeating the effectiveness of April Dunford's Obviously Awesome positioning canvas (must reading for any Product Marketer). With this methodology, you and your team will go through an exercise of defining 'competitive alternative' -- the task here is to identify what customers would use if you did not exist AND to look inwards at what unique attributes you have that your competitors do not. Highly recommend using this as part of your competitive differentiation exercise.
2. Company Strategy -- Many people think competitive differentiation is limited to product. It's not. I like to look at competitive differentiation through a combination of (1) product strategy, (2) GTM strategy, and (3) operational strategy. Often, you can find -- or create -- differentiation in one or multiple of these areas. One way I've put it all together is to develop a 'Buyer Consideration Attribute' map and workshop strengths and weaknesses vis-a-vis competition on the most important attributes. <-- Informed by Blue Ocean Strategy (another must read)
Once you have a good thesis on competitive differentiation, it's time to document it and enable as many relevant teams as possible. Not just sales. Product management and engineering needs these insights to inform their roadmap. Marketing needs these insights both for messaging strategy and in determining other GTM elements like channel, audiences, and more. And then, yes, Sales and customer success needs easy-to-understand and easy-to-take action enablement so they have 20/20 vision of who they will be up against in deals and so they know how to navigate conversations....and win deals.