DVC is a points based timeshare program. You buy a certain number of points (you decide that) and then you are free to use those points at any of the DVC resorts, as well as you those points for other options outside of the DVC resorts (although most will tell you DVC provides the most value when you use them at the DVC resorts).
Since there are so many DVC resorts, one of the first things is to look at all the properties available and try to decide what you might like. Where you buy your points, your "home resort", comes with some advantages. Members get to book vacations at their home resorts starting 11 months in advance of check in. To stay at other DVC resorts, not your home resort, you can start booking 7 months in advance of check in.
How many points to buy depends on when you go, what type of room you want for that trip, and the resort? There is a link at the top to the
points charts at all the resorts. Be sure to use the 2010 points chart (not 2009) as changes are happening starting then.
Unlike weekly timeshares, DVC allows you the flexibility to decide when, where, and for how long you want to stay. Some go 2 or 3 times a year, for long weekends, or others, like me, will go once a year for a longer stay. You are not locked in to buying a specific "week" or a specific "room".
So, if one year, you want to go for a week in December, you can!! If the next year, you want a a longer weekend in the summer, you can!!! All you need are the points!
Of course, in addition to the initial buy in, there are MF's each year and those are dependent on the resort and number of points you own.
As a PP mentioned, dvcnews.com is a great site as well as this one. You will find all the answers you need!
Good luck!