Most of the phillips (or "crosspoint") screwdrivers that I've come across have tip geometry that can be improved a great deal with a little grinding. The simple process shown here probably delivers the most improvement for the least effort, in the largest number of cases... it consists of slightly squaring off the tip with a grindstone.
Step 1: The Problem:
Aside from the poor general machining of most low quality screwdrivers (or bits), there's one particular oddity that degrades the functionality of even some pretty decent ones -- the fact that the tip comes to a little bit too much of a point, to where the blades actually effectively become a cone that prevents the tip from seating all the way into most of the screws you will come across. This is a problem, for instance, when trying to remove a stubborn or frozen screw, and instead of turning it, the screwdriver merely destroys the head of the screw, making removal vastly more difficult. Note the picture inset showing how much of the blade is being kept from seating in the screw head due to the excessively pointy tip.
Step 2: A Proposed Solution:
The quickest way to improve the "grab" of most screwdriver tips is to carefully grind away a small amount of the tip. It may intuitively seem like this would make the screwdriver useless for small screws, but since the portion being removed has no ability to turn a screw, it really just makes it less useful for puncturing things. You don't want to use a powered grinder, since you want to remove (usually) less than a millimeter. The best thing is a fine diamond file, or a sharpening stone. Some fine sandpaper on a block will work if you're carefull not to shred it. Most normal files are too coarse to drag smoothly across the tip without snagging. In any case, you want to grind it squarely, without rounding it off, and the easiest way to do this is to place the grinding surface perpendicular to another flat surface, and slide the screwdriver back and forth while resting on that surface, holding it securely and close to the tip.
Step 3: The Result.
Shown is the subtly squared tip, showing a distinct "X" in the cross section. This is what grabs the screw, and what you want to end up with. If in doubt, try it with a screwdriver you don't care too much about, periodically checking the fit with a few different types of screw heads as you grind it, and stop when you notice a distinct improvement in fit. I would be interested in feedback from other people as to whether they find this situation to apply as generally as I do, and from anyone who can explain why most screwdrivers sold suffer from this "pointy-ness" problem (is it just a matter of quality control? are they designed for ideal screws that no one manufactures?) and I hope this helps prevent a few mangled screw heads. If someone knows of a reason why this is a bad idea, please comment about that, too. Happy screwing.