money, time, energy, vinyl, inspiration...... Did I miss anything? Haha. For real though, the most important thing is probably picking the sample. Try to pick something that is simple yet interesting enough to keep the listeners attention. Edit the sample so its in 2, 4, or 8 bars. Then I usually chop the sample into zones (4, 8, or 16 usually works well). After that, you can program them onto pads in the order that works for you well to play them, rearrange them, and freak 'em. Decide on your melody, lay your drums down, and VOILA!!! Dope ass bangin' beats, just like you can see here
http://www.StudiobHipHop.com
Hope this helps