Well the good news is that you can in much the same way as you can repair your own car or build your own house.
So it really depends if you want to spend the time learning but before you dig into SEO you will need an understanding and a certain skill level for the following:
If you have these then our How to SEO your website pages will really provide you with everything you need to know.
Your only issue is if you can spare the time to do it properly compared to how else you can earn money.
So, for example, if you are a doctor earning $1,000 dollars a week treating people and we give you a SEO quote for $1,500 to optimise your website and you feel that it would take you two months to learn how to do it yourself then the maths speak for themselves.
So once you have got your head around what SEO involves feel free to contact us for a SEO quote and then you can weigh this up with your own situation.
I'm Tim Hill, a Search Engine Optimisation and Online Marketing specialist. I created this site to help others understand that SEO is not a mysterious black art!.
If your a newbie try the Getting Started in SEO page, otherwise feel free to dig around and learn more.