It might be a sickness, but I like making barrels. Generally I'll start with a drawing of what the barrel measurements/threads are. GMB has offered their gunsmith blanks marked on the chamber, muzzle, and some are unmarked. It's best to see which end has the most runout as it's the muzzle end. Sometimes one end will have a rough chopsaw cut and that is usually the chamber end, but it's best to measure. From there I center with a pin gauge in a 4 jaw chuck to face the ends and centercut them with a center drill. As long as the barrel is centered the tailstock doesn't have to be centered as the bit will still want to cut a 60 degree taper. It's usually best to take a skim pass between centers. I use a chuck mounted center in the headstock and a live center in the tailstock. You can use a faceplate and dead center in the headstock, but it's faster to just center the chuckable center. Mine has a step on it so it cannot be pushed back into the chuck. If making a stepped barrel you'll have a more ridged setup if you only have the section of barrel out of the chuck that you're working on. For contoured, steady or follower rest if you're getting chatter or deflection. You get a feel for speeds and feeds which will be different from start to finish as the diameter changes and also different between bore sizes (wall thickness) and alloy. If you get chatter the best advise I was ever given was to get ahead of it or behind. It doesn't happen often, but occasionally you'll get a barrel that just wants to chatter. I change the depth of cut and feed rate until it stops. For me, HSS is much more forgiving than indexable carbide in a manual machine. Usually I'll turn a barrel with indexable carbide, but when I get one of those barrels that wants to chatter I switch back to sharp HSS.
Few pics. Start of a uzi barrel from a GMB long 9mm blank that has been skim cut between centers. M72 Mossberg 375 blank being turned between centers (ended up making it octagon so it wasn't really needed). Centering an AK barrel for chambering using a pin guage. 1891 mauser barrel with blue tape used to support the barrel while chambering and threading. A few completed AR barrels