How to increase my PR?

Lately a lot of blogger’s blogs being demoted in their page rank, some even drop from PR4 to PR2, including my blog too. At first many of us think must be some thing wrong with Big G but check in so many check page rank website, proof that our blogs really been demoted. Now, shall we just accept the fact here and do nothing to increase our page rank? Frankly I really no idea how to increase my page rank, I need to check with my online buddies who are expert in this field. Some of them told me to look for company like website optimization firm to boost up our blog traffic as well as the page rank. One of the well known website optimization firm is ThinkBigSites.com. They able to help us achieve our target and get our blog rank well in search engine company like Big G. I think I better study more about website optimization thingy first before I hire them to assist me, else my blog will forever in PR2. Bear in mind, lower PR hard to earn money from blogging too. Shall I continue using this blog or open a niche blog? As I know niche blog will be easy to maintain since we only blog about certain issue which relate to our niche topic. I better spare some time do my homework now.