There isn't an effective vaccine for malaria, but there are chemical prophylactics, so we took mefilquinone pills. We took one a week before we left, one while we were there, on Saturday, and then one a week for a month after we got back. We were also pretty careful about using repellent during the day an mosquito netting at night.
The pills made us feel tired, and our dreams were strange (apparently this is common among Peace Corps volunteers, as well). Other than a temporary dip in blood pressure, we avoided any of the more severe side effects, like hallucinations or psychotic episodes. We didn't mind missing out on those.
A villager might well sleep on a woven mat no more than an inch thick, not much softer than the dirt floor. Katie was used to it by the time we were there, but that was another of the many Lankan experiences we denied ourselves.
Eastern toilets, however, are not always avoidable. Western toilets do exist, but if you prefer them it's probably best to use them when you find them, rather than engage in an urgent search later.
They are essentially bowls mounted directly into the floor, often with raised, foot-sized surfaces placed conveniently to either side. All in all, they are no less sanitary than their western counterparts, but a little more skill is involved. One squats over the bowl and performs the business of elimination. Males obviously have some advantages in this, but billions of women get by with them every day.
This is probably a good time to bring up the subject of toilet paper. It is not common except in tourist areas, next to western-style toilets. You can generally only buy it in stores catering to a foreign clientele. Without going into too much detail, it's considered socially awkward to touch someone or eat with your left hand. If you want to insult a taxi driver, slap his cab with your left hand...
The idea is that you shouldn't eat something in front of someone else without considering their feelings - they might be hungry or thirsty themselves, and you would make them feel worse.