Tensioning rear wheel? Tensioning a front wheel is - at least in theory - very simple: Go around and tighten each nipple by e.g. a quarter turn. Then re-adjust trueness if necessary. 

I guess if I'd do the same to a typical road rear wheel (with freehub / 10 speed cassette), it would loose the 'dishing'. Is there a rule-of-thumb for this, e.g. something like "3/8 turns on the drive side, 1/4 turns on the other"?
If you are just tightening it up, you should not have a problem keeping the same rules as the front. When you are assembling the when is when the hard part comes, as far as keeping the hub aligned properly.

I wouldn't suggest doing a 1/4 turn all the way around on either wheel. The spokes all come lose at different rates and for different reasons. My suggestion is to go through and get all the spokes evenly snug, barely past loose. If there are snug ones don't turn it at all, if they are loose, turn it 3 or 4 full times if it needs it, just get them all roughly even, but no need to loosen any if they feel too tight, that is for later.

Once you have them all barely snug, go through another time and tighten them up to proper spec tension. In the bike shop we had a torque wrench for the nipples, but if you don't have one, just tighten it up to what feels right. They don't need to be nearly as tight as your axle nuts, they will strip pretty easy if you over tighten them.

If you want to true them, it is best to use a stand, but you can tape a stick to the forks, or just use the breaks as a rough guide. Tighten the 4 spokes opposite the wobble. Just don't go over board, you could "egg" your wheel.