It doesn't matter which side you do it from, as it will have to leave/return to the battery either way, although I would personally do the ground as it's easier.

Yes as I and "RichieST" said, if you disconnect the battery and put a ammeter in series you can measure the draw.

Anything more than a "parasitic drain" and then you know something is draining it that shouldn't be.

Once you have confirmed this, then you can remove the fuses one by one and check again to see if your figure has dropped, you can then isolate the problem to a particular circuit.

I seem to remember someone saying about a relay which causes drains with these?

Martin