currently Google is the best option but you may also consider some in-text advertising options too. It is not against adsense TOS to have in-text ads on the same pages with adsense ads. The best option for in-text advertising are: Inlinks.com (pays quite well) and Vibrantmedia.com (hard to get into vibrant, they have high website requirements). You may also try Kontera but they pay very very bad, thus I gave up with them early this year.
You can use another PPC advertising programs together with adsense as long as their ads not confusing adsense ads. B the way, suggest to use only adsense since the "alternative" might give negative impact on your adsense earning
You cant beat Google adsense, i see sites all the time with multiple sources of advertising and they all look cheap and nasty, nobody likes a site where the content is hidden amungst advertising, just use google adsense and blend it in within your site.
I don't see a problem with mixing around a bit to see what generates the best results for you and sticking with that.
I am not sure of that. Cus google is the best now. U may try another one but I think that u are not gana get more $$$ that adsense
The only way to know for sure is to test. I'd always use Google first, but others can give you a good ROI.
You can use Google Adsense to make money from ads and some affliate program like CJ or Amazon Affiliates to earn commissions from sales.
You can consider setting up different ad campaigns using different PPC programs for each page or section of your site. Personally as a viewer for a website, I hate having a site too clustered with advertisements from banners to text and popups. So, your not trying to chase away people here, but at the same time you need to manage it properly.
Will I think google is the best for know, but when yahoo and bing combined togather. I think they might beat google