I think it depends on what role you're playing, your pick order, and how talkative your team is. In a perfect world, your teammates will respond if you ask them who they are intending to pick or at least if they are going to play a tank or bruiser or whoever.
Generally I just look to see who my teammates have already picked and I just fill in the blanks. Do we have a tank? If not then I"ll go tanky. Do we have AP? Then I'll go AP. Too much AP? Then I'll do AD.
If I"m first pick, I'll try to see what everyone else picks but if no one responds I just kinda have to go with who I think would work in any situation.
Best thing is honestly....communicate. If you're better on fighters, say that. Tell them that you'd rather play X but think we should have a tank on the team and see if the support can play a tank then or jungler or whoever. Other times you can still win with no tank considering tanks are getting killed fairly fast too