All of the folk in this part of the world are at least competent skiers. The skis are cross-country type, attached to the toe but not the heel. You can ski at high speed downhill, but it's a bit dangerous. If you take your skis across rocks you will ruin them. Getting into or out of skis is a full-round action (note that this is considerably less than the official rules, which say a minute.)
Your move on skis on flat snowy area is 30 (regardless of your normal move). Moving uphill is considered difficult terrain. Moving downhill, your move is 60 the first round, then 120, then 180 for subsequent rounds of only downhill movement. You cannot run or double-move downhill – or rather, what you are doing when you move downhill is double-moving every round, but it only takes a move action, and you can't do it more than once in a round. So, when you are going full speed downhill, your actual move is 90 for the purpose of jumps etc. You can turn angles up to 45 degrees for free at the start of your move or over the course of your move. You can reduce speed by up to 60 for free. Anything fancier requires a Dex check (which is part of the move action):
Turn > 45 degrees at 60: DC 3 (at 120, DC 5, at 180, DC 8)
Stop at 120 DC 3, at 180 DC 5
If you fail any of these checks, you crash: you fall prone, you drop anything you were carrying, you take 1d6 nonlethal damage at 120 or 2d6 at 180, and you lose the rest of your action.
If you bull rush someone while skiing, you get a +4 on your attempt for each 30' you are moving above 30 (so 60 is +2, 120 is +6, 180 is +10 – these numbers are halved because you are double moving as described above). Both parties take 1d6 bludgeoning damage from a collision at 120 and 2d6 from a collision at 180.