So I saw a peavy vrpyr that I wanted to buy on craigslist and contacted the seller on buying on amp. When we meet to exchange the goods, how should I test the amp to make sure everything's working properly? I don't want to go in and just start messing around with the controls and not check everything.
That honestly seems the best way to do it, tweak around with everything
2012 Gibson Les Paul Custom Classic
2001 Schecter C-1 Classic
2007 Yamaha APX500
Vox AC15CC1 w/ Eminence Tonkerlite
Assorted Pedals!

All for sale!

Call me Matt!
Make sure the amp doesn't make any weird noises when it's on, check the condition of the tubes if it has any (don't mess too much with a tube amp), and bring your own guitar to make sure you like the amp's tone. But yeah, other than that, give the amp hell

Oh and a little trick I learned from a guitar buyers' guide: With the amp turned off, stomp your foot next to the amp and listen for any rattling noises.
Lol alright I'll give that amp hell when I get to it.

And the foot thing is a tip I've never heard before but sounds like it'd be a good way to check for any loose parts.