The correct way to ask for a hand job

When you have never seen her before, without a greeting, while breathing heavily and drooling.

Idiot.

You might want to get a few drinks in her first. Some weed if you got it. Then I'd say it depends where you are. In the back seat of your car, parked in a secluded place would be ideal. Then take her hand and start rubbing your crouch with it. She'll soon catch on. Works for me.

I hate handjobs, They don't really feel that good for me and I can't keep an erection while receiving one.

If the girl isn't ready to do more than that then honestly I'd prefer she just let me dry hump her till I cum in my pants.

Unless they are bleeding it might be offensive to some.
If she is your sister it seems way more appropriate.
if she is your sister-in law spending the night and your wife is at work.
if you sported an erection and you both are headed out the door to dinner.
If after 20 minutes she is getting dry and sore but you havent popped.
If she is so short she can't reach around an get a finger in your butt. a handjob will make it easy.
If her jaw is sore and she cant continue giving head.

Do some Italian foreplay: Point to your boner and snap your fingers.

Just grab her hand and show her what it is you want. It worked for me on my sister

Never.