Here’s what I did from PR 0 to 3 in a couple of months.My site:
http://www.mylesagnew.com
Add link on bottom of forum post (including this one)Advertise FREE (Once a week, once a fortnight)
http://freeadvertisingforum.com/
PR5Post in other peoples blog those that have PR2+ rating.As you search for information on the net try searching blogs as well that way you’ll get the information and you can leave feedback (which gives you more backlinks).

*** NOTE only comment in blogs that relate to your site in subject manner and or a product you use this will give google a better rating in the content is relevant ***

I would only recommend advertising in forums once a week and different product or service every post. (Use Different headlines and test and measure)

In sharing this experiment has resulted in a lot of feedback and advice check it out http://www.warriorforum.com/forum/topic.asp?TOPIC_ID=82982

I would recommend trying my way first before buying a product or service that does it automatically or faster.