Glue Boards bigger than need and cut down to size. I usually cut 1" longer than needed.
Example:
The boards we have in the shop are about 5-1/2" wide.
This project requires us to glue some boards up because the board is 9-1/4" wide.
The length is 1'-3" and so I would glue up two boards that are 1" longer (1'4")
When gluing I use several clamps.
2 Spring Clamps (These are so that the two boards stay level with each other. They don't help much with gluing the two boards together.)
2 Bar Clamp (These are what really push the boards together. Make sure they are not bottomed out and that you can acutally tighten them.)