The best way to improve page rank is to build quality links.For this you can use the following techniques:-
1)Get links from the relevant sites.
2)Find relevant blogs and ask them to publish your links or blog rolls for this you can provide them good content for their blogs.
3)You can do directory submission but in less quantity.
4)Increase your followers on twitter.
5)Increase your Facebook likes.
6)Citation is a good way if you are targeting local market.
7)Think according to user and develop unique content in this aspect and market them as you can.
This will help you in increasing the quality back links then your page rank will automatically increase..