+1 on forearm muscles. Rock-climbing helps alot with that!
Anyway, this is what I do:
1. with the bike on the handlebars, loosen the axle nuts and pull the wheel back. Now take your dominant hand and push back on the wheel from the point where the seat-tube meets the chainstays. I usually rest my thumb and part of my hand on the right chainstay (I'm dominant right-handed) and use three fingers on the tire to pull back.
2. You wanna pull back keeping the wheel relatively even and using all the strength you got. With your dominant hand pulling and keeping the wheel even (pointing straight ahead), take your free hand and finger-tighten as must as you can first the drive-side nut and then the non-drive-side nut.
3. Get out your favorite spanner and tighten them a quarter turn more. Now check the chain tension. If you are sufficiently strong, you can get it pretty much perfect with just arm strength. That is, the chain shouldn't feel like it's binding when you spin the wheel. You can check for binding by first spinning the wheel with the chain slack and then spinning it again when you've tensioned it. It probably won't spin as great as when it is super-slack, but it shouldn't look like it's getting hung up.
4. Feel the chain with your hand, make sure there isn't more than an inch of play at any crank-position.
5. Rest the bike on the ground and put it at your favorite skidding/track-standing postition. Now move the cranks up and down and check the play. I usually have about a half-centimeter of play. More than an inch would be dangerous.
6. If the chain tension is good for you, then tighten up those axle nuts and be happy. Otherwise...
7. Flip the bike back on the handlebars and get your dom. hand in the position as before. This time push/pull the wheel to the drive-side and loosen the drive-side nut. The axle should move a bit back and then tighten it. You will notice that the wheel is not centered between the chainstays. Now do the same with the non-drive side to center up the wheel. More often than not, you will have overt-tensioned your chain at this point. You can subsequently play around a bit with loosening and holding the wheel to get the chain to desired tension.
Hope this helps!