Talk to several. Visit them if you can. Ask how long the trust department has been in business, how many trusts they manage, minimum and average size of trusts they manage (most require a certain amount of assets) and how much experience their people have in the trust business.
Compare investment returns, fees (including when and how much the last increase was), and services. Ask to see samples of statements or reports you would receive and see how easy they are to understand.
Facts and numbers are important, but so are the people. Do they seem to genuinely care about you and your family? Do they listen and seem to understand your concerns? Can you understand them? How confident are you that they will be there for you and your family when they are needed?