It's trial and error to start with because you need a good group to choose a good pellet, but you if you can't group you don't know if it's the pellet or you. Best to have a good shot around and they will tell you.
I think batches is the key... if you get a good tin then buy a load of the same batch. For a start it will save you on any price increases further down the road, and you might get a discount for buying in 10's of tins...
BFTA/NSRA County Coach
CSFTA Chairman/BFTA Rep