As long as you pay 100% of your 2001 tax liability if you earned under 150K in 2001 there will be no penalty no matter how much you make this year. If you made over 150K then you must pay 112% of your 2001 taxes in estimated payments to avoid any penlites. Or if you can estimate your income for this year you could pay 90% of your current years liability to avoid penalty. This may be very hard for most traders.
So last year you owed 20,000 to the IRS, send them a check for 5 grand each quarter.
The second concept you should know about is annualization. Simply put, if most of your gains came in December as opposed to evenly through the year you would be justified in paying a large fourth qtr payment having skimped on the other three. This in most cases will trigger a penalty, however if you use the annualization function on most tax software you can wipe this out most of the time.
Finally, don't forget most states with state income tax require you to file estimated payments as well. And their penlites are usually more wicked than the IRS. So it pays to check the safe harbor rules for your State.