Create a site that has original content that's fun to hang out on and you'll get plenty of natural links, and the PR will follow. -Raymond
you can also offer to exchange links, where you provide links to other people's sites and they will do the same in return for backlinking
By adding unique contents continously,promoting it through various available resources (directories submissions,buying signatures at various forums,sponsoring themes,bidding directories submissions etc.). DON.
I don't think link exchange will help to increase the PR and google dislikes this activity and will be beneficial to increase your traffic provided the niches are related. Go for one way link or three way link exchange