I used to carry desiccant to dry out the camera. I have since realized that salt works just as well. If it absorbs a lot of moisture then you can dry it out in an oven. And if you get hungry you can eat it.
I always carry a piece of silk and, if possible, a hair dryer with me when I travel in humid climates. Then I open the camera, cover it with the silk, put it under a chair which I cloak with a blanket (creating an oven-like environment inside). I put the dryer inside (on a low heat setting) and keep one hand under the blanket to make sure the camera doesn't get too hot. The silk protects that camera from dust and dirt. Half an hour will dry almost anything out.
Slides vs. Print film. This depends entirely on your purpose in taking the photos. It used to be that most publications wanted only slides. This is slowly changing - check with whatever publications you have in mind. More importantly, understand that it will be quite expensive to convert slides to prints so there will be a considerable financial barrier to making blowups of all those fantastic shots you took and hanging them on your walls.
Keep your lens clean.
Many experienced photographers take multiple lenses. They certainly come in handy (and are sometimes essential) but keep in mind the following three things:
1) multiple lenses are heavy. You can't take shots with a camera you've left in your hotel.
2) Every time you change your lens you expose the inside of your camera to dust and dirt.
3) Many great shots have been missed because the photographer was busy screwing on just the right lens.
I went to Vietnam with only one lens - a 35-135 zoom. I cannot remember more than a handful of times when I really felt the need for a lens I didn't have, and then I probably wouldn't have had time to put it on my camera. Carrying multiple bodies was out of the question. Most of the time I was hard put to use my camera to its fullest potential.
Manual vs. Automatic camera. This is a difficult decision on a long and rugged trip. A manual camera is harder to operate and slower but is also lighter and less likely to break - and if it does you can still use it (with an external light meter). An automatic (programmable) camera has many useful options (multiple exposure, auto bracketing, etc.) and is much faster to operate. It also breaks down more easily and weighs a ton. In the end I opted for a fully automatic camera (with manual override) and was extremely glad that I did. I could snap off three good grab shots for every one someone else managed to take with a manual camera. Often I managed to get a shot in before my subject saw me and turned away while the manual camera operator was still trying to fine tune his focus. I paid for it with a much heavier and more obvious camera. And I got lucky - mine never broke down.
Small vs. large. Unless taking photos is very important to you, you can buy a small automatic camera that won't break your budget, will deliver fabulous pictures, and will fit into your pocket (and will therefore come along with you wherever you go).
A skylight is absolutely essential. A few filters are useful, especially the workhorses - polarizor and neutral density filters. The others are just toys you play with when you have time.
A tripod can come in very handy for scenics but can be a bear to carry around.
A really good flash can make an enormous difference (see section on tropical light). I used my SB25 for more than half my shots (mostly daylight) to lighten shadows. Fill flash is rapidly becoming a standard part of any photographer's equipment. If you buy a good one then it will do all the light metering for you.
Manuals: Unless you've had your camera for ten years, have rebuilt it twice and wrote the original specs, take the manual along. I didn't, and I regretted it. And if it's a new camera, read the manual before you're on the plane. I didn't...
If you're going on a long trip and photography is important to you, don't take a new camera you're not comfortable with. Sounds obvious, right? I bought my Nikon two months before I left for Vietnam. I was quite sure I would take many rolls of practice film before I left. Somehow errands, preparations, language study got in the way. Camerawork kept getting bumped down the list. In the end there I was, reading the manual on the plane.
Keeping your camera equipment dry is going to be one of your greatest concerns. See the survival tip on drying out gear.
Any time between 9 AMand 3 PM (approx.) the tropical light will take on a leaden glare that will make all of your photos contrasty and flat. Usually I concentrate my photography on the golden moments just after the sun rises and before it sets, and use the rest of the time to scout sites or travel.
Film left in a hot place will deteriorate.
If you must take shots during the midday glare, use a fill flash to soften shadows. This is particularly important in countries where the people wear large overhanging hats. Filters help too.
Always bring a dry bag or some other way to keep your camera dry and out of the dust.
If you must have your camera repaired in a third world country, do it in a reputable place. Then check the innards to make sure they are the same as the ones the camera had when you handed it in.
Cameras and passports are the two hottest items for theft.
Check expiration dates on film before buying. Try to see if they have been stored in a cool, dry place.
Huge cameras are a sign of huge wealth. Be discreet.