Also you should check the manual for tables, which list which skill ranks every class can achieve. Not everyone can become grand master in every skill they can possibly learn. For example, knights, thieves and clerics can learn bow, but only Archers can become GMs in them. Just as only thieves can become GM in Disarm Traps. I learned that the hard way (as in, after I gave my thief, instead of my clerice, the Merchant skill), which is one of the reasons I started over today.
Thiev: BTW, remember to open containers with a party member that has this skill ;)
And buy/sell stuff with the party member that has the Merchant skill (if any of your characters has that one). I always have trouble remembering that.