Looking for TradeskillsFollow

I have a few characters along with my brother and we are wondering what tradeskills to give them. One is a level 12 Undead warlock that doesn't have any tradeskills, a level 10 human warrior with mining and blacksmithing, a level 8 night elf rouge with herbalism and a level 6 tauren druid that has skinning. They all have quite a bit of silver but I was wondering what I could put with each of them that might increase their profit. I use the auction quite a bit with them, selling some raw materials.