Sanding is an essential step in perfecting your woodworking project.
If you don't do it, your finish will likely look awful.
If you do it wrong, you could ruin your work.
So, follow the tips below to get on the short road to success.

1. Use 80 and 120 grit for rough sanding and 180 grit sand paper for fine sanding.
   Open-coat, garnet paper works the best, in my experience.
   I like open-coat paper because it doesn't clog since the abrasives are spaced out on the paper.
   Garnet produces a smoother finish than aluminum oxide.
   
2. Avoid oscillating sanders.
   They tend to leave tiny scratches that show up after you finish your piece.
   Not to mention, the spongy bottom can result in other strange remnants left in the wood.
   
3. Get belt sander skills.
   A belt sander requires a bit more concentration and technique, but it offers much better results than its oscillating cousin.
   Belt sanders have flat metal bottoms, which keep the surface flat.
   Also, they can be used in place of a smoothing plane if you use a low enough grit (60 is best).
   Make sure you use long, full strokes and keep the sander flat against the surface to avoid gouging dips into your boards.
   
4. Play it again, Sam.
   Sand multiple times with grits starting at roughly 80 grit and working to 120 grit.
   By working progressively through the grit levels, your effect on the wood will decrease, but your piece will become smoother and smoother.
   
5. Use 220 to 240 grit between finish coats.
   If you are going to seal or stain your work, perform multiple applications of the finish and send between each application.
   This will give your piece a richer color with a nicer looking finish.
   

Now that you're on the short road, get to the woodshop!