Every one of us wants to rank high in Google. You must focus on backlink building to have good serps. But backlink building has to be done with great care - not to get penalized.
Here are some simple tips which will definetely help:
1. Don't buy (or sell) sitewide links for serps. Buy links from individual pages*.
2. Don't look for high PR links only - start your campaign for a new site with PR 0-1 and slowly move up each week as you see your rankings improve.
3. Control link placement speed. Remember of "Too many links at once" Google filter.
4. Control the number of outbound links on your pages and on pages where you place your links, avoid link-farms, links to gambling, pills, etc.
5. A link from a relevant website is excellent, but a link from a quality site of other niche or other language can also boost your ranking - so don't ignore such links.
6. Make links look natural. Use different link anchors, promote not only your main page, but your deep pages too.
7. Don't do reciprocal linkexchange.
* - Links from individual pages are far more effective when speaking of improving serps, not PR. They are more natural and organic. Sitewide links can easily be filtered.
Selling sitewide links also means loosing lots of money - if your site has 1000 of PR2-3 pages, you could earn hundreds of $$$ a month just from selling ONE outbound link per page, compared to some $20-30 for selling a sitewide link (now, when it has become possible). What do you think?
Using this simple technique, many our sites has received an excellent rank in Google in just 1 month for HIGHLY competitive keywords. If you are interested, I can tell how we did it.
Just remember, that your site's ranking depends on your efforts and skills, it doesn't depend on your site's PR etc. (see our PR if you don't believe it).