| It really depends on what you consider to be results. For instance, having the top position for any keyword really doesn't matter if your site isn't able to convert the traffic into business. In that scenario a good optimization firm would first focus on your site's conversion ability, then on increasing it's rankings.
There are many different questions to ask, but the most important thing for you to know is exactly - step-by-step - what they are planning to do. Then simply have them prove that their methods work and have shown results over several different industries.
As far as pricing goes...expect to spend a minimum of $15k-$20k per year. The more competitive/complicated your site's needs are, the more it will cost. If you are interested, feel free to PM me the site you are thinking of hiring a company for, and I'll see if I can recommend a few different companies. An approximate annual budget would help narrow things a bit, but isn't necessary.
Good luck either way!
P.S. Stay away from anybody that guarantees rankings. No legitimate company offers this for obvious reasons. It may sound good, but there are always a ton of loop-holes that result in you not getting your money back.
-Midgetlov |