in a scenario where most visitors will close the browser and only a few days or weeks later - manually type in the site name and sign up

what is the ultimate way to know which sign up came from which ad?

would it be to match the signup IP which i get in the order form to the unique visitor IP's?

most of my ads are google adwords and i just started using analitics



thank you all in advance for your input :)

If you're using google adwords and analytics in conjunction, the tracking is done automatically by the script you would insert in your website pages, which place cookies in the users' computer to track clickthroughs, conversions etc.