The most important thing to remember when it comes to getting your man off by hand is lubrication!
It has to be wet, slimy, slippery – if your hand gets sticky, it might chaff and this will get you, and him, nowhere.
How you keep his erection slippery is up to you – there are several lubricants on the market, but I would suggest going for a water-based lube instead of an oil-based one. KY Jelly is also not recommended, as it seems to work best with your natural secretions.
A good way to start is to ask your man beforehand how he masturbates. If he’s open enough, he might give you a hint or two on how he likes it.
Remember that his lower erogenous zones are not focused on his penis alone – his testacles can also be very sensitive and feeling you play with them can be very erotic. There is also the anogenital region, which, for some men, is great for stimulation. Apparently the area just below the head of his erect penis on the bottom is also very sensitive, so try that spot as well. Again, every man is different, so try to ask questions as you go along to make sure you’re getting it right.
Another trick is to vary the amount that you close your hand around his erection. Try tightening and loosening your fingers alternately – you’ll know how your man is liking it. Try to think about the rhythm and stroke your man uses when he is making love to you, and attempt to simulate it. Sometimes it’s fast and sometimes it’s slow, but the way your man reacts to your touch is really your cue on how well you’re doing and how much he’s enjoying it.
You can also try to use both hands, as this covers more surface area.
Try to tease him a little with your tongue and your mouth, but since this is a handjob, try not to get too carried away down there!