Just looking at my first pair of boots and was wondering whether it's the done thing to buy half a size up (10.5 vs 10) or just to buy the same as my shoe size?
Try them, heel lift is a killer.
Boots loosen as they age and they hurt when they are loose (heal lift). I go for fitting properly and using snow board socks that are normal sock thickness where they are in the boot (with some extra padding of areas that take a lot of pressure).
Heat molding liners are well worth it for comfort.
Try some get the ones that fit regardless of what it says on them.
You need the correct fit or your feet will hurt and they won't be as responsive as they should be.
Should they feel pretty snug at first then?
I tried some size 10's on and they felt quite tight. Will they loosen a up after a day or two or will it take longer than that?
They should feel tighter than a gnat's chuff when you put them on (but fitting - i.e. no pressure points and not too short in the toes). They will loosen off a lot over the first few runs and will break down significantly over a few weeks of riding them.
As above, mouldable liners are a big plus and I also would consider custom insoles. Good ski shops will do them. I haven't ridden without a pair for 20 years.