Kazmandu,
When you do select an individual or service to help you with SEO, make sure you clearly state your goals. For example if you have a contact page that you want to drive traffic to then make sure a company talks about generating traffic to create leads. Just driving traffic to a site won't necessarily translate into sales. You must have a plan for visitors once they arrive at the site whether it be to call a phone number, fill out a form, etc.
Here are some good tips on converting visitors,
http://seo-entrepreneur.com/content/crossing-conversion-point-how-convert-visitors-customers
Hope that helps,
Shawn