the above is correct, but note that because of the vast amount of article writing goin on, you also have to get links to the articles many times for them to get indexed at all. Even on the biggest sites, your articles will not always get indexed unless you build some links to them. other than that - forum sigs, which are extremely low value and might not give much value at all unless you are the thread starter and the topic is relevant to your site link...and the thread gets indexed.
you are trying the fastest method by using DP as soon as you have more than 10 posts, you are having signature links Other good way is blogging and blog commenting. Social bookmarking is another nice way.
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you have a problem here. You see, the best way is certainly not going to be the fastest, and probably not the cheapest. Concentrate on building up quality links rather than being focused on price and time scale.
I think blog comment links are a quick way to do it. It's not automated (at least shouldn't be), but it's generally quick to do. Make sure to leave a relevant comment and you just might get traffic from the blog itself too.