I had the benefit of advice from buddies who had gotten the shot… When you go to get in line, go to the front and tell the tech you’re getting GG, and you’d like to warm up the vial. Take the vial back to the end of the line and roll it between your hands until you get to the front. Makes it slightly less painful…
i didn't get that advice, and I never noticed anyone fondling their vaccine vial at the shot clinic. In my cases -- twice -- the shot wasn't what I'd call painful. I had a knot on my arm for a day or two that caused some tenderness, but no pain to any real degree. i've had flu shots that left more of an impression, hurting each time i used my arm.
Yellow Fever, OTOH, was a bitch! I found out why they only gave that one on Fridays. So "victims" wouldn't miss any duty days. Instead, they lost their weekend to lying in bed with a fever and sweating their proverbial ass off! But, when Monday rolled around, we were good to go.
i think the best preventative is to massage the injection site before the shot, and try to relax as much as possible.
The best advice is to always keep your shots up to date. You really don't want to be in the deployment processing line and have to get half a dozen shots all at once -- and at the worst possible time. If there's any pain, fever or other negative effects, better to not have to suffer them when mobilizing.