I recently made a copper tubing coil to use in a solar-powered water-boiler and learned the right way and the wrong way to bend copper tubing.  The tubing is easy to bend when making large-radius curves, but is likely to kink or crush when trying to make smaller-radius bends.  I learned that I could avoid those problems by filling the tube with salt before bending.

 

Here's what I used.

.25 inch Copper pipe.  5 feet long

1/4 cup of Salt.  (Fine, dry Sand would also work)

Tape

Funnel (or makeshift funnel)

Vice

Hammer

Hard Cylindrical Objects of various diameters.  I used a 3" diameter steel pipe and a 1.5" diameter socket-wrench socket.