I think the best first step for me personally would be asking more questions of friends (with strong convictions) of different denominations. I admittedly approach other faith traditions with a less than fully open mind (as most Catholics do) but when I have asked questions, I find more similarities than I had initially expected to.
Another strong step is to learn more about your own faith tradition, though it may seem counterintuitive. If you’re able to answer questions about your own faith more confidently, your dialogue with others will be that much deeper and more helpful to both parties. You can debate better and find whether your argument or theirs can stand up to the scrutiny it will face amongst less friendly company.
I also believe reading books written by other denominations can be a way to improve your relationship with Christians of other traditions! Its understandable to not be too eager to risk offending a friend with more sensitive questions- a book with a distant author can fix that situation!