Skills are rolled on 4dF. If multiple skills apply to a situation, use the highest applicable skill. This applies to everything except magic, where you use the lowest applicable skill. If a skill or attribute is complementary, you may use its XP to aid you in your task.
Fumbles
A result of –4 or worse is a fumble, which means you not only failed, but screwed up. A natural roll of –4 is also a fumble, even for those with very high skill. Fumbles are not necessarily horrible. You can recover from a fumble by risking a Confidence point on re-roll. You may also choose to spend one XP to salvage the fumble, but you must make that decision before the GM tells you what happened.
Modifiers
Experience and Confidence can help you in some situations. See the attributes section.