A few guidelines for making an easily navigable request topic, and hopefully get the attention of more hackers to your request:
(This is a guideline --- you are free to add or remove things depending on the request, but please try to make it easy to understand.)
First, you need a clear and concise title, like "Shadow over Sonic".
You can just stay with "Shadow" if you're not sure who you want to put him over.
What you need to give in the topic:
These are the bare minimum.
- The character you are requesting. Don't say "I want a character done in Brawl. Anyone interested?".
If your character is an original character, mention it.
- At least one reference picture (Or a link to the model rip you want to see imported). The more of the character or stage is visible, the better.
Large pictures should be put into spoilers.
- (If applicable) What character you'd like it over.
Now, if you want to make your request much more interesting, take a few minutes to check if there is a model rip of your character somewhere on Google. Or at least a texture rip.
The first one will act as the best kind of reference ever, and the second one can be used directly to texture the vertex/model. That way, the generous hacker who's going to take your request should have an easier time making it.