Just a way to turn a little extra profit your way.
32 commons = 8 uncommons = 1 rare = 1 ticket
There are a large number of exceptions to this rule. Many commons sell for 4 per ticket, depending on supply/demand. Many uncommons sell for 1 per ticket, and a few of the more useful uncommons sell for up to 3 tickets each. Rares sell for up to 20 tickets each, although most of them are worth only 1 ticket.
If you're just looking to acquire a bunch of cards, then just look for the people who are selling for better than standard rates. Many people sell commons for 40+ per ticket, uncommons for 16+ per ticket, and rares can be found for 2 or sometimes even 3 per ticket. Usually, the most useful cards are not found in such selections, but I've found lots of things I can use this way.
However, if you're designing a deck in advance, and then looking to acquire those cards specifically, then you'll have to search for the cards you want. Just look through people's collections that sell at standard rates to find your commons/uncommons, but to find your rares, you'll have to search for those rares specifically, and pay whatever the cheapest price you can find them for is.
Feel free to PM me if you have any more specific questions.
[ 08-14-2003: Message edited by: Mog 1.0 ]