If you have to pick up by the tail, do it at the base right next to the body. De-gloving (the skin coming off) is a risk, so it is best done quickly. I bred rats and never had to pick up by the tail, I typically pick up around the rib cage area. If you are afraid of being bitten, IMO, it is better to use gloves and pick up around the torso of the rat (gently no squeezing) than picking up by the tail. I'm not sawing tailing is awful, but it is uncomfortable for them and IMO, I want the rat as happy and calm as possible in this scenario.

Breeding your own feeders or buying from someone who does will also go a long way in getting calm animals. You want to purchase from someone that culls biters and breeds from calm easily handled stock. Rats from the pet store aren't ideal, unless it is a small shop that breeds their own, as the big mills don't really care about temperament when breeding and you can get some pretty sketchy animals. If a breeder heavily culls for temperament, over several generations, you can achieve calm animals that won't bite unless you cause them pain or scare them. This is ideal, but takes time.

I've been bitten twice, both maternal aggression cases. Bites are no fun and I would much rather be bitten by my boa than a rat.