I'm surprised he didn't mention that you often need to leave a small amount of bearing play on a hollow axle hub, because tightening the skewer can take up the slack - if you don't leave it loose you can have too much preload and shorten the life of your hubs. If you have part worn hubs and can't get them to adjust without tight spots or loose spots, leave them slightly loose, they'll last longer while you wait for new cones or new hubs to arrive.