First off, you won't break it on the first day, mistreatment of valve amps will lead to the tubes wearing out quicker, they won't just break, so don't worry! How I do it:
Turn it ON, leave standby OFF for 2 mins for homepractice, but as long as possible before a band practice or a gig: the longer the tubes have to warm up before they have to be worked hard the better, the first thing I do at a gig or band practice is plug mu amp in and warm it up whilst i set pedals up/tune up etc. When you want to play, flick standby ON and you're away! Opposite way round to switch off, but without so much of a wait, turn standby OFF, then leave it maybe 30 secs before flicking it OFF; I don't know if this acctually matters but I generally get a loud 'pop' if I don't let it cool a little, maybe its just my amp?
And all glass is more delicate when its hot, leaving it 10 mins before lifting and stuff is a good idea but I'm sure you can wheel it out of the way! Notice the next festival or gig you go to that the roadies will move valve amps last unless they are on castors? Basically its making your valves last longer, and the better they are looked after the longer they will sound good for!
Hope that helps!
