There are many ways to optimize your website for search engines. But there are just as many outdated ways that you may have heard of and should stay away from...
Keyword Stuffing...
In the late 1990's pages were stuffed with keyword they wanted search engines to find.
Instead:
Write your page for people, don't use jargan.
Make sure that the keywords are in prominent parts of your web pages like headers, subheaders, etc.
Search Engine Submission...
Many companies still offer this service, and while it's not necessary it doesn't hurt your ratings, there's no need to pay someone hundreds of dollars for this service.
Instead:
Write good content aimed at your target audience.
Add a link to your site from your Social Marketing accounts like Facebook, MySpace and Twitter.
Link Exchanges...
There are many websites that offer link exchange schemes promising your link will appear on thousands of sites. Having websites that relate to your website linking to you is a great way to increase your optimization, but if you are found to be part of one of the link exchange schemes your site may be severly penalized!
Instead:
Offer testimonials to business you work with asking for a link back to your website for a great review of their services.