I'm still a newbie in Skyrim but here is a tip I wished I had known. I play a hybrid mage and have light armor in all the spots but the chest where I have a robe that has magic regen +75% and some other stat. Well, I put a point into the Light Armor Custom Fit perk which gives you a bonus if you have light armor in hands, head, feet and chest. Well, robes aren't considered light armor so no bonus.
Also, my son showed me a nifty trick. Grab a bucket or cauldron and pick it up and put it on the merchants head. He will be blind and you can steal everything right in front of him without having to sneak. I don't know if you can pickpocket him without getting caught, though.