If you look at the random orbital sander from the bottom, you will notice that when you turn it on, it will jitterbug around in a circular motion giving you a nice uniform finish.
It is very important that you remove material equally from the entire surface. This will eliminate cupping and uneven surfaces.
The best way to achieve this is to take a pencil and lightly draw a scribe line back and forth across the entire surface.
As you proceed to sand the entire surface, you will see the pencil marks disappear. This verifies that the entire surface has been sanded.
After passing the sander over the surface, it still may feel or looks rough. Simply repeat the pencil scribing and re-sand the entire surface. Repeat until you are satisfied with the job.
Sanding can be a very dusty job without a filtering system. Most sanders today come with a built-in filter system but better yet is to hook it up to a vacuum system removing the dust right out of the area.
It is important that you always travel in the direction of the wood grain. Never overlap your sander more than 1/2 the diameter of the sanding pad.
This also applies to the end of the material travel as well as the edge of the material travel. By exceeding the 1/2 way mark of the sanding pad, it makes it very easy to round off your edges which you don’t want to do.
When sanding, do not add additional pressure on the sander thinking you will speed things up but actually you have a tendency to slow the sander down causing scratch marks. Allow only the weight of the sander to do the job.
When starting and stopping, it is important to start up and stop the sander when off the surface to eliminate surface scratches.