The head of a mans penis is usually the most sensitive part of his equipment. This is a good thing, since a woman who knows this can control his level of arousal by where she chooses to focus her attention.
When giving your man a handjob, always begin with plenty of lubrication, then warm up your hands by rubbing them together. As you begin to stroke him, alternate your strokes from the top or head of his penis to the base or shaft. In other words, rather than a single stroke moving from base to head to base again, give him shorter strokes that focus solely on the head, then as you sense his excitement level rising, switch to strokes that stay down on the base of his penis.
This is particularly helpful if your man has a tendency to come too quickly; your ability to switch the focus to the base of his shaft slows his pace and prolongs the pleasure.
On the other hand, if you increase your attention to the head of his penis when youre ready for him to come, youre bound to get results in very short order.