Just some advice from somebody that's been doing this since March. Everything that meathead and freddy has said is true. I'm at the point now where I'm getting sales organically for the first site I launched, which was in the weight loss niche.
It was a good niche to get my feet wet, but it's too saturated now. Get creative. My 2nd site is in a completely unrelated niche. I don't even mess with my weight loss site anymore. It's just there quietly collecting commissions.
Once I switched niches and applied what I learned from the weight loss niche, my income increased very nicely. Be real. Be personal. Get people to optin to your list. Work that list. Treat this as a business. It's not something blackhat to do to make some quick coin. It's certainly not quick money. You will put the hours in. Hours and hours and hours of mind-numbing commenting. Day in, day out. You can't automate it and you won't see a return for awhile. You stop commenting, income stops. You won't see a future. Then a few months go by, and the organic traffic comes.
I won't ever reveal my niches, but they are out there. Pick a niche that you enjoy, that you're knowledgeable about, and use that to your advantage. Sell yourself. Once people trust you, that's gold. People buy from people they trust.
I see various people's comments, and I already know which ones are successful and which ones are just making it harder for everybody else. The shitty spammers who don't know a thing about marketing made the weight loss (and many other niches) much, much harder to make it worth your while. They don't last long, because eventually they give up, thinking that the method doesn't work. The method absolutely works, they just suck at marketing. The unfortunate part is that they're little annoying little cockroaches. As soon as one quits, 3 more takes its' place. That's the ultimate reason why I switched niches (so I guess I should be thanking the cockroaches?).
Be original, be creative. Read every damn thing you can on the actual science behind marketing. I'm not talking about reading internet marketing blogs, but the actual psychology behind selling. Start reading up on NLP.
If you're not willing to put some thought behind your campaigns, then you might as well just not even start. Ads aren't written on the fly. Ads take hours, sometimes even days, to write. Every word is carefully thought out. People aren't that dumb. Start treating your potential visitors like they have some shred of intelligence.
For instance, I did a quick search for weight loss, to find a comment that one of you recently left:
"Nice Idea for lazy person and I'm find a better solution for lazy person..3 Easy Ways To Lose Weight Quickly : [domain was here]"
What the hell kind of comment is that? Nobody is going to click on that. It had very little to do with the article (other than it was about weight loss itself). Why are you just trying to spray and pray with your comments? Take your time with your comments. Ya know, actually comment on the article! Read the article, leave a relevant comment.
Lastly, some of y'all really don't grasp what this is all about. You're using url shortener services as your links, or you're leaving obfuscated text-based links. Why would you do that?? You want to get organic traffic, too! Otherwise you'll have to comment daily to keep the traffic up - forever. Organic traffic is where it's at. Stop with the spam tactics. Spamming kills it for everybody - yourself included.