The very first stage in setting up your Ad Network participation is showing other people's ads on your site. To do this, you will have to have made a decision on which ad format you want to display and how many ads you want to serve up at a time.
Anchor Text Only ads are nice and small, inobtrusive to the rest of your content. You could put it under a header saying 'Sponsored Links' or something similar. You can format these the way you want as well. Some put them in the footer with hyphens between each ad. Others choose a verticle alignment in their navigation menu.
Remember that the more ads you show (up to 5 per page count towards your weight) the more weight you get. Like for like, remember?
Text Banners take up more space but are more user friendly because of the description below it. Some people think of this as free dynamic content which could have positive effects for their ranking.
Graphic Banners are more prominent which can be good and bad. It also ads to the page load time more than the text based ads do.