Starting to test ride

[kerryhb]

I have read how important a test ride is when shopping for a new bike and I am hoping to start tomorrow. My question is, what should I actually be doing on the test ride? I am thinking varying speeds, shifting, braking, etc, as well as fit and overall comfort, but what else should I be noticing or looking for? I am currently riding my MIL's old mountain bike, so I have a pretty clear idea of what does not work for me, which I think is helpful. Does someone from the LBS come with you, or is every shop different? If you were test riding a new bike, how would you structure your ride? Total beginner here so any/all advice is very much appreciated. Thank you!