I'm sure everybody has their own pet method, here's mine!
I usually start with new brass, so I don't have to contend with differences from combustion residue from the powder or primer. If your brass is really clean from tumbling for a decent amount of time, you should be OK for any purpose other than benchrest competition.
I perform all prep steps--sizing, trimming, primer pocket reaming, flash hole deburring. If it is virgin military brass, I also swage the primer pocket.
I then begin weighing, after all of the brass has been "uniformed".
I weigh a few and get an average, then accept a certain range either side of the average.
For .223 size cases, I accept .5 gr. either side of the average.
For a .308 size case, I will accept 1.0 gr. spread either side of the average.
These uniformed and weight selected cases are bagged together and only used for my long range loads for competitive shooting. For 200/300 yard shooting, for my High Power competition purposes, I haven't found weight selected cases are needed. With no sorting, or prep, I can still get 1/2 MOA with proper load development, which is more than adequate for High Power competition.