You can check the link popularity if it is gaining. Check the keywords you were working on- where they are ranked in SE. You may check the traffic also.
You can also check PR, but whatever you do, don't report this to the client as a main measure of success, because it's not kept up to date and thus is very unreliable.
Type your keywords in Google and see where you rank. When you get where you want to be, then you're done.
You should have made the report in prior before doing seo work. but still you can check out the effect by following ways Make report of the keywords and check them in the search engine like google or yahoo.. Check the pr Check the back links, this will help you to know how much back links you have gained with the seo work. Make a submission report every month on what work u have done and what result it gave to you... Hope the above tips will help you....
Check your site in Google, for its ranking & traffic. backlinkwatch.com is a great site for checking backlinks of the site.
I guess checking the real effect of your SEO for your site takes for about 4-6months... At that time, you'll clearly see if your SEO is worthy for your site... you could also do IBL check, SERP's, visits form time to time but still, it takes a long time to see the real effect of what you do to your site...