I will show my cards for a few reasons. If I limp reraise , or limp call with a strong hand and the guy folds I will show sometimes to let everyone know I use that play. That way in the future I can limp with suited cards and they wont raise me out. I will show a hand were I check raised from blinds when I flopped a strong hand if they don't call. This shows them that I defend my blinds, so stop trying to steal and that I trap. By them knowing I trap I can then get cheaper draws because they know I trap. I show a few hands to improve my table image of being tight and not raising with trash. I show strong hands on buttons from time to time to show that I'm not stealing in position. Since I am aware that I am giving this info out I switch up my play so its hard to tell. I have found that its easier to bluff after you have set up a solid table image that gets respect, by reassuring there reads from time to time makes them more willing to fold and give you respect for a hand, especially if you show them the same betting patterns when you had the nuts.