How can I increase my website's PageRank in google

Create links to your site. How you can achieve this is by regularly posting on forums and adding link to your site in your signature. Another way is by regularly posting useful comments on other peoples blog. Be sure to add the link to your site as you post comments. Be sure not to spam. Also with this method you'll be able to increase traffic to your site.

get more links to your site from other sites that already have a high(er) pagerank