One good site that I know of is www.hodstock.com Their CM/MC section is pretty good. It definitely doesn't hurt either to get the Prima strategy guide for Frontiers. There is a really in depth description of every ability attainable in class mastery. Some abilities are available at level 1, some 10, 25, etc. Most have a base stat required (i.e. Brawn 1 requires 100 STR) The four subcategories are archetype, racial, general, and...can't remember last one. You set your class mastery XP% as you wish; if you get 100k xp and have it set at 50%, u'll get 50k xp and 50k cm xp, and so on. With debt, half xp goes to debt automatically and it is calculated from there. Honestly, it is a lot easier to get the jist of in game than it is to explain it.