Ad-Aware has been around for over 10 years. It's highly trusted, but over the years Ad-Aware is both essential and not enough.
The program will scan your computer for infections, and the more data on your computer, the longer the scan will be. Though you can set it to custom scan at different levels and single areas to speed things up. It is common for an infection to be so smart that it will crash Ad-Aware when its caught, but more the average infection, Ad-Aware does the trick.
There are also a lot of plugins for Ad-Aware, however, some plugins require the full version for use. I found the VX/2 removal tool useful since that is a common pest, and one of the hardest to remove.
Everything else is pretty basic in the program. Just as scan and remove. Additions like the skinnable user interface could be fun if you are bored.
Only thing to really emphasize here is that you should update your definitions file before every scan to be sure you remove the newest pests as they spread around the Internet and onto computers.
Don't be surprised at the large number of "cookies" found on your computer during the scan, as these are very common and mostly harmless. Real adware and spyware is what you should be concerned about.
Please note that if you find that you have multiple real infections, it is likely that you could have even more that Ad-Aware was unable to find. Have at least one more security program scan your whole PC just to be on the safe side.