Me too, i think google adsense works best for me and i will continue to use it on all my website. It is convenient and effective. Some ppc company like chitika can be included together with google adsense to add extra income for your website and it is no harm adding extra potential income to your website.
The first question you should be asking is where do the people you want to reach do their searches. Far and away, Google has the lions share of the search market. That being said, Yahoo, MSN, and Ask all have PPC programs that can be profitable. They just will not return the same numbers of total clicks. Google will, by an order of magnitude, produce more clicks. And hence, more leads.
The second thing you should ask, is "What is a lead worth to me?"
When you have an idea what a lead is worth, you can bid your keywords accordingly. Sometimes it takes a bit of historical data, ie. how many clicks at what price turned into leads , before you can put a value on a lead. There really is no shortcut to learning that information. Make a best guesstimate, and tweak as you go.
PPC program adwords is the best,but have you consider PPV Marketing,I have try this one and I have to admit this service lower my advertising budget ,PPV that I use is directcpv perhaps you should check that