after that dont ask questions until you've jumped in and tried it. i didnt learn shit till i actually started running campaigns and figuring out what works what doesnt. longtail is king. broad phrase match will suck ur wallet like a cracked out hooker sucks ur dick (at least until you understand it). content network is for suckers (again until you understand what works on it).
For PayPerClick campaigns, you can use Wordtracker to see what keywords are most searched. Just google it and look for the free version. Other PPC providers have such tools to help you decide which to bid on.
Don't just rely on using top keywords for your PPC campaign - this is the reason why others are failing. Bidding on top keywords will yield you less as competition for these are stiff already. The technique here is opting for other long tail keywords that is more likely to yield specific results because specific searches on long tail keywords or phrases are the ones that usually convert. Those who employ such search are more likely to buy IMO.
Also don't bid that high at first, weigh first what keywords convert in your niche after a test run so you will know what works and what doesn't.