1) read and learn all you can about ppc
2) start with one campaign and set budget at about 4x the payout (some people like to set it at 2x or 3x, i prefer 4x to make sure its a dud or not even if i have to take a slight loss, because sometimes after period of time multiple sales can come at once or be delayed)
3) tweak and make it more profitable (learn this while studying ppc by reading)
4) expand it to other traffic sources (more keywords, more ppc networks, etc)
5) go back to step 2 and start with additional campaigns
there are 2 camps of people, some rather use free marketing techniques, others prefer to pay for traffic.. i prefer ppc. less work before you actually notice results. i say if you have the funds, paid traffic is the way to go, and if not, obviously free is the way to go. the best is always a combination though.