Making a sign or poster

An undoubtedly stupid question here, but how do I make a sign or poster? If you can point me to a tutorial or resource I'd be extremely grateful!

1. Create the sign in a program like Photoshop.
2. Save in JPG or TGA format.
3. Upload it to SL.
4. Create new prim in world.
5. Apply new texture to prim.

Aaron more or less said it all.

A couple of things to add...

it costs L$10 to upload the file.
The file should be a power of 2 pixels on each side, 32, 64, 128, 256 etc. For a sign bigger than 256 seems unlikely unless you're tiling them. The texture doesn't have to be square though, 32 X 256 would give you a nice banner type sign shape. If you don't make your sign to this sort of size SL will resize it for you. It does many things nicely, but PS does the resizing (if necessary) better, and making your sign that size to start is even better!

Many thanks!!