setting gain using a dmm

I'm planning on using a DMM to set the gains on a four channel amp using a test tone.

Is it safe to do this without the speakers hooked up? I'm concerned with turning the power up on the amp without a load on it. I've done alot of reading about this but haven't seen a answer to my question.

The other concern I had is, if I left all the speakers hooked up, and checked one channel at a time would the test tone at high volume damage the speakers?  

you can have a load on the amp. but there's no need to. it will not damage the amp if you do or if you do not. the test tone shouldn't hurt the speaker no. unless you run the amp into a heavy clip at high power.