Some sites prefer to just link with text but others link with banners. If you are artistic you can create your own banners. Banner Exchange Services . . . If you are going to utilize your web site to promote your existing business or services then it can become a very effective tool. Also be very skeptical of the Infomercial programs that offer overnight profits on start-ups if you buy their web site development packages.
Networks pay by impressions, click-thru's or commission on product sales.
An impression is an exposure to an ad that is placed on you page. This means that every time someone visits your page your are paid for the exposure. Click-thru's mean that the visitor has to click on the banner for you to be paid. And commission sales require a visitor to not only click on the banner but it also result in a sale. Before you sign with an advertiser it is important that you do some investigating.