Good technique for squaring-up hardwood edges?
You don't say what saw you used to cut the wood, but if you use a tenon saw you should get a cleaner cut in the first place that requires less sanding. This is because the saw has finer teeth for a smoother cut and a stiffening spine that means you get a straighter cut.

Clamping a second piece of wood to use as a guide is another alternative.

Alternatively you could use a plane to remove the excess wood - but make sure that you clamp a piece of scrap wood to the end of the plank to avoid it splitting:

------&gt; direction of plane
+---------+---+
|         |   |
|    ^    |   | &lt;- Scrap
|    |    |   |
|    |    |   |
  direction of grain