For film camera users, how much film should you take on a trip? A good generalization is two 36 exposure rolls (three 24 exposure rolls) for each day of the trip. This might sound like a lot, but it will allow you to take several shots in special situations. Besides, if you have film left over after the trip you can always use it another time.
When packing film for a trip, take each roll out of its box, but leave the film cassette in its plastic canister. This takes up less space, and you'll have less garbage to throw away.
If you'll be shooting a number of rolls of film on your trip, you'll want some method of sequencing the rolls. Don't do this ahead of time. It would only mess things up when you bring unexposed rolls home.
The following method of sequencing works well. After a roll has been shot, place the cassette back in its canister, but first, with a felt-tip pen, mark the cassette and the top of the canister with a number to indicate its place in order. For example, the first roll would be marked #1. If the film canisters are totally black, making it difficult to see any markings, place a small piece of masking tape on the lid to mark on.
If you shoot digital, make sure that you have enough image space to cover the trip. Generally, digital image cards come in 16, 32, 64, 128, 256, and 512 megabytes, and cards are available in 1, 2, 4 and 8 gigabytes, and beyond. The last batch of cards will hold several hundred images, if not thousands of pictures.
I would recommend staying within the first group of digital cards listed in the above paragraph because the larger capacity cards are more expensive, and if something happens to a card (and things do happen), you'll not only be out the money you paid for the card, but you might have lost pictures as well. Rather than buying one large-capacity card, buy two, or even three, of those with lower-capacity. These can be numbered so you'll know the order in which the cards were used.
As a generalization for travel photography, consider buying enough cards to cover 80 times the megapixel rating of your camera. For example, if you have a 6 megapixel camera, buy enough cards, or a card, to cover 480 megabytes of memory.
Another way of determining the amount of digital space you might need for a trip is to buy enough megabytes for 40 pictures a day. For a 10 day trip, you would need a card or cards that would give you at least 400 megabytes. This would mean getting a 512 megabyte card. A safer bet would be to get two such cards in case the trip is extended, you decide to take more pictures, or for insurance against something happening to the first card. The more digital memory space you have, the more apt you'll be to take pictures.
The better you plan for your trip, the more you'll enjoy it. Take plenty of pictures, and we'll be anxious to see them when you get back.