To deter thieves:

1. Don't put bullhorns, risers, deep v's, or anything else "trendy" on it. Remember, most bicycle thieves are normal dudes looking for "sick rides" or expensive parts, not necessarily just homeless dudes.
2. If you have a brooks seat, run some old chain through it and connect it to your top tube. Ain't going nowhere. Or toss a plastic bag over it when you know it will be prone to thieves.
3. Strip paint. You can actually probably do this yourself.
4. Take used motor oil and dirty up parts. Not moving parts though.
5. If the frame is really crappy, you could wrap duct tape or gaff tape around the joints or tubes... make it look like the tape is essential... like it's THAT ****ty of a bike.

These worked for me. Good luck.