Setting up your bubble
Forum speechbubbles work through clever use of the imgleft and imgright tags. I think they're pretty easy to figure out, but for anyone who gets confused, here's what you do.
In order to get the main image to display to the left of the text, you're going to use the imgleft tag at the start of your post. And in order to get the end bracket to display to the right of the text, you're going to use the imgright tag,
also at the start of your post. Imgleft and imgright both have buttons up above the post box. You can also include those two words in brackets. It works the same as the image tag, syntax-wise. Here's some example code that you can use as a template. Remember that you can change the font style however you like!
[imgleft]Left image's URL[/imgleft][imgright]Right image's URL[/imgright]
[center] Text goes here. [/center]
Text formatting
It gets pretty annoying to keep copying and pasting your speechbubble code for every post, doesn't it? Well, if you're using Firefox, you may want to check out Tektek's
Gaian toolbar. It takes up an annoying amount of browser space, but you can hide it and still use the text formatting part! Totally useful - I definitely recommend checking it out.
I don't think there's anything similar for IE. Sorry, but hey, why are you using IE in the first place? ;D
Centering text
One thing that I've noticed is that people sometimes have trouble getting their text centered in a speechbubble, without having the text drop to below the bubble. I don't know why this happens, but I do know how to fix it.
Okay, so Gaia has two different kinds of tags for centering text. One is the [ align=center ] and [ /align ] tag set, and the other is the [ center ] and [ /center ] tag set (only, you know, without the spaces - take 'em out when actually using as code). Unfortunately, the first set is what you get when you use the formatting options that show up above the posting box. This will look fine in Firefox, but it will put the text below the bubble in Internet Explorer. The second set of tags, however, will put the text up in the right place in both browsers. So! The moral of the story is to use [ center ] instead of [ align=center ]. ^_^