When bending some materials that can be elastically deformed (such as steel), bend past the desired bend angle; due to elastic recovery, they will spring back slightly to the desired angle. To make sure that the bend angle is correct, either do some research and figure out the angle you need, or just keep bending and checking in small increments.

Bend in the right order. You want to make sure that after every bend, you are still able to securely fixture your workpiece. If you don't pick the correct order of bends, you'll end up with bends that you can't reach with the brake, and you'll have to do the rest by hand or with a custom jig. You may also want to design your part with this consideration in mind.

Account for bend radius (bend allowance). When you bend sheet metal, the material does not bend at a perfect 90° at the bend line. Rather, it forms a radius that can usually be estimated as 2x the thickness of the sheet metal. Instead of trusting me, find a bend radius calculator online. Adjust your bend line and cuts accordingly.

Use bend reliefs when bending thicker materials. Otherwise, tears or unsightly deformations may form at the corners of your bend.

For certain materials that are brittle or hard, such as acrylic, you may need to heat the area that you are bending, or anneal it before bending. Talk to Drew before you do this.