This is what I do:

1. Sit on you knees next to your bike close the the chain
2. Grab the handlebar en move your bike just off the sidestand..(close to upright)
3. Take two fingers (index and middle finger) and put it between the chain and the fattest part of the swingarm (close to the front sprocket),

If you cannot get your fingers in - the chain is too tight
If you can move your fingers up and down between the swingarm and the chain - the chain is too lose

Quick and easy test...

my 2c