I was following this tutorial on making a map:http://hce.halomaps.org/index.cfm?fid=1974
and when it came time to texture, I think I did everything right, but the textures didn't show up on my model. HELP!

When you are in the material editor (hotkey=M) and you make a material then apply what bitmap you are using, click the white and blue checkered box. When you check this, the material uses the diffuse bitmap or texture you aplied to to the it. Without it checked, it will use the diffuse color (yours should be set to gray by default, unless you changed it).

If you did check this make sure the material is actually apllied to the model. You can do this by draging the material bubble onto your model.

If both this is done, make sure you apply the UVW Map modifer is applied to your model and select box(you could select others, but this is probubly what you want. You could also UVW Unwrap it, but I wont get that in depth into that)

If none of this works I am not quite sure what is wrong. I hope this helps.

I don't know what I did wrong :( someone who can help, PLEASE DO!

Did they not show up on your model in Max or ingame?