Thunderst wrote:lad, you are the DM your word is rules
Word. Though, if you want tips for remembering some rules... A way that I always found that helped is think of a way to make the rule make sense in a gameplay scenario before it comes up. A general rule of thumb is difficulty changes by 5 for each step of Hard. So, climbing a rough rock wall is 10, say, while climbing a plain rope is 15 (or 5 if it's a rough wall with a rope).
So, say, if you want to make a ruling on a player that wants to climb a chandelier's chain/rope so he could swing through combat and slash some face. Without looking at the tables, I'd say that's a 10 for climb DC (rope and wall, but it's not a Climbing rope, and it's old, so it could be harder to get a grip), and swinging from one end of the room to another, slashing as he goes, would be either an easy strength or Tumble roll (DC 5, to make sure you hold onto the rope and don't flair around too much). Attacking would be like a charge (+2 to attack, -2 to your AC), except you don't need to worry about blocked movement lanes (since you're on a frigging rope).
The premade DM screens usually have quick tables for a lot of the difficulty scales too, so that may be worth looking into.
Depending on the edition of D&D, this may be handy too: http://www.d20srd.org/
It's the core rulebooks for 3.5, along with the Psionics and Epic handbook rules.