Hi there,
First of all, all back links are NOT created equal! Google has a certain criteria for evaluating back links.
1. The back link should come from a reputable website: no link farms, porn sites, gambling sites, sites with pages under construction, sites with more than 100 other backlinks posted on them.
Ideally you want to have back links on other sites that have similiar themes and content as yours - they should compliment eachother.
The ideal backlink should be a 'text' link. This means no image links.
In obtaining text links, try to get the webmaster to agree to letting you have a backlink which includes a keyword or key phrase that you are trying to optimize your web pages for, in the linking text. Using your domain name as the link text won't help you very much. It's better nothing but try for the optimal link.
Do some research to see if you can find other sites with complimentary themes to yours and approach the webmaster by email or phone if you are able to get a contact# from the website.
Be very wary of firms that advertise that they will do your backlinking for you! Most do not understand what a quality backlink is. Their services tend to be very cheap and well . . . you get what you pay for :-)
It's too important to let someone else screw it up for you.
Don't add a whole bunch of backlinks all at once. It raises a 'red flag' with Google.
Don't add a whole bunch of backlinks that come from one website. Google likes to see backlinks pointing to your website from a variety of different websites with a a variety of different IP's on different "C" blocks.
Try posting to forums in your niche where they allow you to add a link to your posts that points back to your website.
Posting to blogs is another great way of generating backlinks. Just make sure you observe the blog rules for posting comments.
Try writing articles and submitting them to article directory sites. Sites like www.ezinearticles.com allow you to create a "Bio" at the bottom each article you submit that can have a link back to your website.
When articles you write are very popular, you'll find that they get picked up by other webmasters, added to their sites for their visitors to enjoy. Each time they do this, your link back is included, affording you more opportunities to generate backlinks.
Finally, quality is better than quantity. If your competition has 600 backlinks, it doesn't necessarily mean they're all great. If you had a 100 quality backlinks you could easily get more points from Google.
Hope this helps.
Brad