Commonly overlooked rules, Important or Not, tell them to me! Options

[MadLetter]

Hi folks!

I'm currently starting up a new Shadowrun Campaign set in Halifax/NovaScotia and have already gotten the first run behind me. I've been out of the system for quite a long time, roughly one and a half year, but kept informed and up-to-date with books. We use the "new" SR4A ruleset (which is the reason we began again, the book just made me want to play again very badly, they need to do more books in fullcolor!).

Sooo... I'm reading through the whole thing again, but I think you all know that you easily skip one or two rules. One example is that I simply forgot the +2 to all Matrix Actions modifier for being VR (read it after the game on these boards). I'm putting together an exhaustive rule-guide for my players - one for Normal stuff (shooting, tests, melee, car-chase-combat, ...), one for Matrix and one for Magic each.

So the question basically is: What are rules you often overlook, that are forgotten for this reason or another, or simply hidden away in text somewhere? Would you help me to make my rule-guide for my players?

Thanks beforehand!