There are three basic elements to a Font tag - size, color, and face. For example:
These tricks are helpful for highlighting specific points of interest beyond simply CAPITALIZING them, making them <b>bold</b> or <i> italicized </i>. There is a tag for <u>underlining</u> text -- but DON'T use it ... underlining is used to indicate a link, and will likely confuse visitors when it isn't a link. There is also a tag for text, but, as you can see, it's highly annoying and SHOULDN'T BE USED. If you can't see it, well, that's another reason for not using it -- not all browsers recognize that tag.
Most computers will recognize three basic fonts: helvetica, roman and arial. The latest versions of Netscape and Explorer will be able to display these as well. AOL, well, AOL is the bottom end for all 'special features' so don't worry about them further than making sure everything shows up in AOL in a recognizable manner. You can experiment with other fonts that one or the other browsers may not support, like comic sans ms or desdemona, but you should build your font tag so that if the browser doesn't support it, there is one that it does as backup. That looks like this:
<font face="comic sans ms", "roman">
For graphics, choosing a font should be based on both function and design, ie: will the font you choose not only match the overall aesthetic of the page you are building, but also remain legible and understandable no matter what size it is, or what filters or colors you apply to it in the building of your graphic? If the answer is no, don't use it, no matter how cool it looks.