How to remove a leech
Leeches are common in rainforests of Madagascar, mainland Africa, and Southeast Asia. Unlike leeches in other parts of the world, rainforest leeches live in leaf litter and vegetation -- they are not aquatic. They find their prey (you and other warm-blooded animals) by odor and sound vibrations. In leech-rich areas, if you stand still for a few minutes, you'll see leeches dropping from vegetation and moving toward you like inchworms.
Terrestrial leeches are generally small (although they can get quite huge in some parts of the world) but will gorge themselves during a meal, gaining up to ten times their weight. The single feeding will be enough to sustain a leech for several months.
The best protection against leeches is covering up and using insect repellent on clothing, although they are extremely persistent and invariably if you spend enough tromping around in the forest you will get leeched. Do not get overly concerned about a leech attack -- they carry no disease and there is low risk of causing significant blood loss. Leech bites do not hurt -- since they release an anaesthetic when they sink their teeth into your skin -- but they do bleed profusely. Leeches use an anticoagulant when they bite to facilitate the flow of blood from the wound.
Removing a leech
If you are bitten by a leech and are compelled to remove it before it has had its full (leeches drop off on their own when they are done feeding), you can do so by following these steps:
In the case that a leech invades an orifice like your nose, ear, or mouth you have a slightly more serious problem since the leach will expand as it fills with blood. If you have access to strong (drinkable) alcohol or hydrogen peroxide you can try gargling (if the leech is in your mouth). Worst case scenario you may have to puncture the leech with a sharp object.