First Fixed project!

I want to start building my first fixed wheel bike myself. starting with buying a used frame is there anything i need to look for when buying a frame to turn into a fixie?
also does anyone have a cheap frame 54cm going?
thanks

You need to look our for a frame that has horizontal drop outs (the bit where the rear wheel sits in the frame).

The reason you need the drop outs to be horizontal and not vertical is that you need to be able to pull the wheel backwards to get the chain nice and tight before screwing the bolts down.

Have a looky here (scroll down to 'drop outs')

http://www.sheldonbrown.com/gloss_dr-z.html