If there is an axiom of woodworking, it is that nobody really likes hand sanding. With the advent and subsequent improvement of power sanders, hand sanding really isn't the chore that it used to be. However, there are distinct benefits to breaking out sheets of sandpaper and "putting some elbow grease into it." As you'll hopefully discover, the benefits are worth the time and energy spent, for no matter how good of a job the best power sanders can do, they still can't beat the finish of a final hand sanding.
The Tools of the Trade:
Sandpaper comes in 9" x 12" sheets. I prefer to cut them in half long-wise, then take each half and cut them in half in the opposite direction. This will leave you with four pieces at a 4-1/2" x 6" size. Wrap one of the pieces of sandpaper around a sanding block and you're ready to get to work.
There's a Right Way and a Wrong Way to Sand:
As with every task, there's a right way and a wrong way to hand sand. The most obvious thing is that you always want to sand with the grain, not across it. Keep the flat side of the sanding block in complete contact with the surface of the wood. When sanding with the grain, it's OK to get close to the edges, but exercise caution that you don't inadvertently round over the corners. If you want the corner to be softened, use the sanding block to sand a chamfer to the edge.
When the surface appears to be fully sanded to the desired finish, set aside the sanding block and, with a fresh piece of sandpaper, lightly sand by hand applying light pressure with the fingertips. Clean the surface in preparation for finishing by removing the dust with either a tack cloth (available at woodworking suppliers) or a clean cloth with mineral spirits.
Before sanding end grain, run your fingers along the edge of the end grain. You should notice that one direction feels smoother than the other direction. Sanding in the smooth direction will yield better results.