Different loading manuals often list different maximum powder charges. This is why you want to start low and work up - there are many converging reasons why this is a good idea.
Here's a (very) general rule of thumb I use for bullet seating...
If the base of the bullet is seated below the bottom of the neck, start paying close attention to pressure signs.
More specific bullet seating lore -
Ammo intended to go into a magazine must be short enough (duh!
). For reliability and because of differences in magazines, I'll seat bullets 0.020" - 0.030" shorter than what just fits into most mags. Shorter/lighter bullets for the caliber will probably not be long enough to have magazine issues.
Ammo that does not have to fit into a mag can be as long as you like, so long as it chambers OK for your purposes. Be careful if you're seating into the lands... you
probably don't want to do that.
If the bullet has a crimp grove (cannelure),
AND the bullet is intended for the particular caliber you are loading, then seating to the cannelure is a safe bet (308 vs. 30-06 military bullets have the cannelure at different places, for instance).
Seating a bullet one caliber deep is a pretty good rule of thumb. I've never run into pressure issues by doing this. Seating much shallower than that and you have to be careful when handling the ammo so as not to dislodge bullets. Seating deeper will not give you a better grip on the bullet.
Seating a bullet so the ogive is below the case mouth is seated too deep. This one's a pretty hard & fast rule.
Seating a bullet so shallow that you can move the bullet with your fingers is
probably not seated deep enough.
Have fun & be safe!