What is the best way to stretch paper?

I assume you are doing watercolor? If so, 140# paper needs to be stretched. 300# paper, on the other hand; is so heavy that it will not buckle even with the sloppiest washes. 300# paper is expensive though. I have been using staples on a fiberboard for my 140# paper. I am not happy with this process though because it leaves the deckled edges unsightly. If you are framing the piece with a mat, it doesn't make any difference, however; because the staple marks will be covered by the mat.

To stretch watercolor paper, you want to soak it flat in cold water for 10-15 minutes. You will then want to let it drip dry. I have children's hangers with the clamps for holding pants. They have enough tension to hold the paper, but not enough to mar it. I let the paper drip off for about 10 minutes, then staple it to my board. When I staple, I start from the middle of each side. Put a staple in the center of each side first, then move from the center out on each side. On a full sheet (22"x30") I will use 8-10 staples on the long sides and 5+ on the short sides.

There are others who use bulldog clamps and styrofoam board to stretch their paper. I have not tried this.