Adjusting rear chain

I use a spirit level with a laser beam in it. Surprisingly cheap too. Hold the level against side of tyre and shine beam forwards on to floor at side of front wheel. Do it on each side of the tyre and you will see straight away if the wheels are in line. 

Ian

... to the chain engaging on the sprocket as you spin the rear wheel, that will tell you if you have it right.  Above is as good as any as long as you can see past the centre stand...

Cheers

Jon

To get the centre stand out of the way I use axle stands under the footrests.  It also allows some of the weight to be on the rear wheel when you're checking the free play.