The main method of trading for
DVC members is request first where you don't give up your points until they find the trade you want AND you say OK. There is no way to know for certain about low, mid and high season but you can get an idea by looking at II's website and common sense. Anything that is not red time should be low season. For red time, it's only the peak time that's high season.
You won't know for certain how many points it will cost (contrary to popular belief) until you find a match but you can get a good idea and get historical information. It's really pretty simple though you need to plan well in advance, like 1-2 years for the best alternatives. But it can be a costly option for all but the top choices in both resorts and seasons.