The extreme weather of the regions close to the equator can be potentially dangerous without the correct approach. Cover up from the sun with clothes and sun cream. Protect your eyes with pharmaceutical sunglasses - Boots Pharmacy do a pair for £10.
Don't attempt climbing mountain passes during the hottest part of the day. Take long breaks between 12 - 3, use this time to rehydrate, eat and admire the setting.
Read into the season, certain roads could be impassable in the wet season. The direction of the wind is a huge factor for cycling. Fortunately and coincidentally, we were with wind going down the coast of Vietnam. Some days we would barely peddle as the breeze was immense. I couldn't imagine doing some of these stretches in the other direction! This website also can give an insite into wind directions...
As inexperienced riders we didn't consider researching the topography of the regions we were in... We paid a big price for this by struggling on huge inclines with bikes lacking the right gears... Use this website for an indication of the areas mountains!