A smaller graphic is less noticeable than a larger one. Banners with such calls to action receive substantially higher click through rates. Consider the background color of the site where you plan to advertise. Choose a color for the banner that stands out as opposed to blending in. Keep your banner fresh by replacing it often.
Fresh banners receive higher click through rates.
Find out what kind of traffic the site you are considering for advertising is getting. A banner on a site with no traffic is relatively useless. It's like a billboard on a road that no one takes. Ad rates vary in price depending on a number of factors, including whether the page is generally targeted or more focused on a particular audience, the size of the banner, and the number of banners featured on a page at one time. Net Marketing includes articles on the subject as well as a guide to Web site pricing, a glossary of terms, and an online forum and bulletin board.