To get a good PR....
Comment on high PR dofollow blogs...
Contact high PR blogs and ask for link exchange (I did this when I had PR 2 and im really lucky... got a backlink from a huge site! Now, I have PR 4!) ...
Do not link to low PR sites....
Don't put too much links on your site....
If you are selling advertisements from your site, then the PR is very very important! People come for that!
Do not do too much SEO... it will make ur PR to drop... Once my PR went from 5 to 2 and gave me a heart attack! The advertisers stopped flowing in.... But now, its back to 4

So, be careful when dealing with the Page Rank!