where can I advertise my AD for free to get more clients for my small business?

You can print fliers and put them up at local apartment complexes. Many larger complexes have bulletin boards for free ads in the area where mailboxes are located.

If you have a website, there are several pay-to-click sites that have click exchanges where others will visit your site based on the number of times you click other members' links. To find legitimate PTC sites, visit http://ptc-investgations.blogspot.com/.

A website is a great way to market your business and the products or services you offer.

Check out printing sites like Vista Print--they make window decals for your car, printed pens, printed notepads, and thousands of other advertising items. It isn't free, but the window decal on your car would be a low cost way to begin.

craigslist, stores, facebook, myspace... Google blogs and classifieds where your type of clients go. You may be able to post free ads, or responses to inquiries on those pages.

Twitter:

Sign up to Twitter with a catchy name, and then sign up to "Twollow" here you will get a 7 day free trial of their services.

Twollow allows you to add in 5 keywords to search other users and become followers of them. The idea is they will then follow you. This doesn't always happen, but will a great deal of the time. From there you can advertise to your followers.

If you're posting links use bit.ly.com to shorten your URLs

I suggest this be part of your online campaign, not all of it ;)

The twitter site is twellow.com , which Tom Razoo mentioned. Definitely Social Media sites are a good way to go. As well as you can Google Free classifieds.

I find that preparing press releases as much as you possibly can about your services is a great avenue to find potential clients. There are a number of free press release sites that allow you to post the release, THEN THEY MARKET IT FOR YOU BY SENDING IT TO ALL THE CRAWLERS FOR FREE.