For seating depth, with most bullets I try to get as close to the lands as possible and call it good. With monometal bullets such as Barnes bullets, I let them jump a bit.
As far as shots in a group goes, I use 3 shot groups. Understand that a 3 shot group is much less statistically powerful than is a 5 shot group so, if you get a real good 3 shot group, don't assume the load is fantastic until you do more testing. On the other hand, if you get a bad 3 shot group, you can probably safely assume that the load isn't that good and can go on to something else.
You can save a lot of ammo by shooting 3 shot groups for testing rather than 5 shot groups.