First of all you check your website's OnPage SEO and then move to the back links you have created, because after Google last update you must have to follow algorithms. Because Google become little strict to stop spammers.
Here are some techniques you can use for SEO,
Onpage: Unique Content, Keyword Density, H1 Tag, Meta Keywords, Title, Description, Image Optimization, etc..
OffPage: Article Submission, Web Directory Submission, Social Book Marking, Web 2.0 Creation, Social Media Marketing, Classifieds, etc...