Is it better to charge a laptop when the battery's almost gone of when there still a lot of it?

Modern Lithium-Ion batteries (the most common type in modern laptops) really doesn't care.

Many people seem to remember the old Ni-cad batteries from last century that had a hell of a "memory effect" and are still used sometimes in things like cordless phones or cordless tools.

Now, if you are still using a laptop that uses NiCads, I recommend upgrading to something at least equivalent to a Pentium II; something capable if running Win98SE or System 8.
The last NiCad laptop I saw was a Powerbook 180, and NiCads were on the way out for laptops even then. Assuming that you bought your laptop in this century, it doesn't matter.

However, just for the sake of maintenance, you *will* want to run it down once a month or so just to recalibrate it to account for wear and time. Whether you use it or not, an LiON battery *will* degrade over time. However, the number of charge cycles doesn't matter except as it pertains to temperature (charging heats up the battery... unless the charger cuts off, as most do at a certain point).

I could g33|< out even more on the specifics of battery technology until your head spins, but the underlying point is that it doesn't matter.

It depends on the type of battery. Ni-cads should always be fully discharged, but other types are not as sensitive.
http://tldp.org/HOWTO/Battery-Powered/battery.html

drain it as much as possible than recharge it...

It is best for the battery to let it drain as much as possible before charging it.

It's best to let the battery die down before completely charging it.
My IBM allows me to charge my laptop only when it reaches a certain percentage (that I choose), even when it's plugged in, and how far to charge it. Your laptop may have similar features or you probably could find similar sofware.

its best to keep it charged because it gives the battery a better chance to not store so much memory power

I just leave it plugged in at all times, using it or not.

i have heard one needs to drain a battery five times and recharge it each time so that it will hold the charge for a long time. who has that kind of time. all i know is the sooner you can recharge your battery the better. you never know when you will be able to recharge it again.