Assuming this post rebuild or post reassembly...
Safety first.
Safety glasses. Everyone should own these, no one wants to be blind.
Wear earplugs, its going to be loud. Don't put the last one in until she is started. listen close during cranking.
Fire extinguisher - I don't have to tell you why. Yes experience is golden.
Kill switch. Make sure you can shut it down fast if something sounds wrong.
Personally, I always install a basic set of gauges. oil pressure, temp etc. You can get basic cheapys almost anywhere. Yes I have a set of sunpros, they work for bench testing for "yes/no visual indicators". Get mechanical so its easy to "wire them". Trust me it sucks if the oil pump isn't working and you don't know it.
Prime oil pump - yep this is critical. Verify oil pressure gauges registers your prime.
Fan on radiator if you have it on for some time.
No alt? Have that battery fully charged. With alt, keep clear of those moving belts!
Chock your stand wheels. She will "walk away" when she hits high idle or a lumpy cam.
Resist the urge to rev. Yeah, I see them do it on TV too, resist. Let it follow a normal warm cycle etc. so you can see what it does. Manual choke, you are on your own. That is what you are doing it for, right?
Don't sweat smoke, But pay attention. There is normal smoke and abnormal smoke. Learn to identify which is which.
Ventilate: it may be cold outside where you are, but don't kill yourself with carbon monoxide.
Buddy system: Don't do it alone. Have someone (anyone) nearby in case you need "help".
Randy
Side note: I had a friend who did a rebuild and rebuilt the carb and made some mistakes along the way. She started right up and ran badly, he went to rev it (getting close to the carb), I guess he misinstalled the secondary jets and the timing was off, it backfired into the carb when he revved it and the flame nailed him. He was alone and no fire extinguisher in his garage. I'll just say he needed a trip to the hospital.
Let's be safe guys.
