I have tried to build the most important tips into the rest of the guide, especially in the sections: RTW Packing List, Planning & Preparation, Health, Email, Contacts, and Companions. These are some tips that couldn't fit in the rest of the guide, or I would like to emphasize.
I would like to stress one thing before you go: you can never drink too much water. Saving money on water is no savings; you will know what I mean if you ever have a kidney stone. Worse, dehydration can lead to a pancreas infection. You have a built-in dehydration indicator: the color of your urine. If you are dehydrated and drink a liter or two of water, you will notice it clear up within a few hours. Don't wait until you are thirsty. Drinks containing caffeine (coffee, tea, soft drinks), alcohol, and high levels of sugar (soft drinks) are not good replacement fluids because they are diuretics, which cause even more fluid loss.
Always carry food and water on buses and trains. Besides the usual delays, there are places where the food along the way doesn't look so appetizing. Also, especially if you are alone, you might not want to lose your seat, nor risk your transportation leaving without you, or with your bags still on the roof!
The key to staying on schedule is getting up early and going to bed early. The majority of transport starts out in the morning to get there faster. This also allows you to arrive early and find a good hotel room, and leave enough time to see more of a place.
In tropical environments, go to bed early like the locals, and get up early to see the most fascinating event: everyone starting their day at sunrise. A side-benefit is that you will experience more of the culture you came to see, instead of staying up late partying with the tourists.
Once every week or two, eat at more expensive restaurants to get an appreciation of how good a country's cuisine can really be. The street food is basically cheap fast food that anyone can cook, and tends to taste the same.
If you bring good clothing, do your own laundry, otherwise your clothes may turn strange colors, not always get so clean, and not last very long. I had many shirts and pants scrubbed or beaten to death, especially around the collar!
Towel-Rolling Technique: If you have time, let clothes drip for awhile. To dry clothes faster after rinsing, wring-out as much as you can, then spread the item out on a large, dry towel. If possible, wrap the towel over the topside. Get as much of the towel in contact with the garment as possible. Roll the towel up and twist as tight as possible.
You will make many friends while travelling, and will probably also visit them when you get to their country. Likewise, they will probably want to visit you. When you are given contact info, save it online, or write it down, then send the original pieces of paper home by airmail every month or two. I have seen many people lose their addressbooks, making it impossible to visit or contact anyone they had met.
If there are things you are interested in, or become interested in, start collecting them early. This doesn't mean just buying things. I wish I had photographed many things, especially the huts in rice patties, and sketched the way they were built. I also wish I had spent more time watching people cook things, like the many varieties of banana pancakes that I cannot seem to replicate.
Some tried-and-true ways to prevent or minimize burnout: Travel slow and with a purpose. Stop every now and then. Learn the language. Avoid Western tourists a majority of the time. Don't drink alcohol. Go to bed early, get up early, and guard your health. Don't live too cheaply. Have people to visit. Don't have a family that guilt-trips you over family obligations!
Air Pollution is something to consider when planning the length of your stay in many major cities, and in some regions. Smog from cars, chemicals from industrial processes, pollen, particulates including smoke, agricultural dust, desert dust, and home generators in small towns. Become familiar with PM2.5 levels and lung cancer rates. Winter is especially bad in many places due to temperature inversion, which is like a blanket that keeps most of the pollution concentrated close to the ground, spiking from sunset until well after sunrise. If you have asthma or other respiratory issues, the rainy season is a good time, since the rain scrubs the air; otherwise, budget for air conditioning, spend less time outdoors, and find ways to reduce time there.
Swimmer's Guide to Pools Anywhere in the World