We consider five major "cost centers" for our trips:
Lodging
Airfare
Car Rental
Dining
Spending Money/AP's (if needed)
We own DVC, so lodging is already budgeted into our monthly payments - and we use our debit card for as many of those bills as possible, since we earn a mile for every dollar spent.
Airfare - is paid for using the debit card as soon as we find the right deal and have the extra cash available.
Car Rental - saved in advance and the money is in the debit account when we arrive (double miles on this one!)
Dining - we know in advance how much so we save and as with the car rental, the money is in the checking account ready to be spent.
Spending money - this is generally $100 cash for each week we're there, $50 in ones for valet, mousekeeping, etc tips, and $10 in quarters for tolls. Everything above and beyond that comes from saved money on our debit card.
We have multiple checking accounts, so before we leave bills are paid from one account and vacation money is in the other account. We have done it this way for years now and we love it - we do have a credit card for emergencies, but we have yet to use it. We make sure we can afford to spend every penny we have available in the "vacation" account, so anything left over (and yes, we do have some leftover - poor planning on my part

) is money we can then apply back towards "real life" again.
I need to know everything is taken care of before we leave and that we won't suffer financially when we get back or I can't enjoy our trips.