paying taxes on online poker

For all you taxpayers out there:

Can someone pay taxes on winnings by simply writing the dollar amount in the blank for "income from business, investments, etc" which is usually used for 1099 earnings? Or are you required to attach a log of dates played, locations, winnings, etc?

This brings me to my next question, if you know how much you have made in the calendar year but do not have specific logs, what would be the best way to proceed?

Thanks for any comments or suggestions.