Adding the natural extention to Pam's statement:
1) Always use Banked points from last year first.
2) Always Bank Points as early as possible
3) Only borrow from next year the minimum points you will need for this year.
4) Expect to want more points, regardless of banking, borrowing and how many points you buy at first.....this
DVC thing is addictive.
To expand Terry's Point:
(assume 150 pt buy-in)
Year 1: Bank 150 points to year 2.
Year 2: Borrow 150 points from year 3. With banked points, your total is 450 points for use in year 2. Go on big DVC trip. Take me with you.
Year 3: Do nothing. You have no points for year 3 left.
Year 4: See Year 1
Year 5: See Year 2...esp. the last sentence.

Year 6: See year 3.
Repeat until 2042.
Of course, at some point you might decide that going every year on a smaller trip makes more sense...or you decide to add more points since you can't possibly live without Disney at least once a year, if not twice.
One unsolicited piece of advice....read as many threads here as you can...you'll see questions asked you'd never have thought to think.
Hope this helps,
Joe