I don't quite understand michaelwlf3's post.

Does he have too long a chain or too short a chain?

For myself, I buy a KMC 610 chain and it comes out of the box way too long.

I put all the parts in place, including the chain and a mid-size sprocket (in my case, 17t), and make note of where I have to break the chain in order to make it a little too long.

I break the chain at a length, where, when I put it on with the master link, I will have some slack.

So, I put on the chain with the master link and look at it and think about it for a full minute.

At that point, I seriously consider whether I can break the chain again and have enough chain to use my sprocket of choice, with the axle halfway between its full travel, aft and forward, in the horizontal dropouts.

If I have any doubts, I don't break it again.

With the chain on the bike, I pull the wheel and axle back until I have no visible slack.

No visible slack.

I tentatively tighten everything down and then I place the pedals in all the clock positions and check the chain for tension throughout the full rotation of the crank.

I look for a half inch up and down (total) without any effort (two fingers mildly pinching the chain and wiggling it).

I spin the crank and feel for a totally liquid movement.

If it doesn't feel totally liquid, and if the wheel and crank won't spin forever without any input from me, I loosen it a hair and try again.

I use a cheap Sugino/SR chainring from Harris Cyclery and I use only EAI cogs because I find them both consistently round.

I have also centered my chainring using the Sheldon Brown method.

In the end, I have a silent chain with no visible slack and no resistance to spinning.

It helps to use chaintugs.

I use two MKS chaintugs and I get silent, liquid movement with no slack.

The no-slack part give me a greater sense of control, especially at very slow speeds.