Malaria is transmitted by a specific type of mosquito (female anopheles) that breeds in still / stagnant water that collects after monsoons. If you're travelling during winter or summer in India, you don't have to worry about this too much as the weather conditions are not conducive for these specific mosquitoes to breed. Locals usually don't take malaria pills, instead preferring to sleep in mosquito nets that will prevent you from getting bitten regardless of what type of mosquito it is. Most mosquitoes you'll get bitten by (and you will) are harmless.
While most travellers going to take precautions against malaria, another mosquito vector-borne disease that is common in India is dengue. Compared to malaria, dengue is a bigger threat as it's harder to 'prevent'; there are no pills or vaccinations for it. Like malaria, this is also transmitted by a specific kind of mosquito (aedes aegypti) locally known as 'tiger mosquito' as it has yellow-striped bands on its legs. If you see such a mosquito, then you know to be extra careful.
City and town authorities take disease control seriously and frequent fumigation is carried out during monsoon season; you will be fairly safe when if you're stick mostly to cities when travelling. It helps to keep an eye on local newspapers if you're travelling for longer periods for news about dengue outbreaks. Take extra precaution when you're staying near places with stagnant pools of water, such as the nature reserves, backwater lagoons et al.
Long story short: Sleep in a mosquito net, or burn a 'mosquito coil' (ask for it at any convenience store; it burns slowly and releases smoke fumes that keep mosquitoes away. Handier to carry around than a net, but fragile so no point buying in bulk as they will break when packed in bags). It will keep you safe from malaria/dengue-carrying mosquitoes and every other kind.
Most government health organizations recommend that chemoprophylaxis when traveling to an area where malaria is endemic (which includes South India). However, you should do whatever makes you comfortable - ideally after discussing it with a travel doctor. When I was in Delhi, it was primarily during winter and my travel doctor told me that for that area at that time of year, it really wasn't necessary for me to take anti-malaria pills because there was virtually no risk of contracting malaria then.
Malaria season is whenever there are mosquitos - basically, when it's warm/hot and there is water around. Monsoon season is the highest-risk time for malaria, typically May - October. I was in India from January - May and only took Malarone for about less than half that time (middle of March through the end of my trip in May).
You should also discuss with a doctor with type of anti-malaria pills are best for you; there are pros and cons for the convenience and side of effects of all the varieties available. (The biggest difference convenience-wise is taking a pill once a week is easier than doing it every day, but many people have stronger adverse reactions to the weekly over the daily. Again, discuss with your doctor what is right for you - any travel clinic can help.)
Depends on where you are planning to go, and when. If you are travelling to cities, you should be safe. In most urban areas, people are at a very low risk due to Malaria. Most cities have some kind of mosquito-control programme. If you are travelling to the hills, forests, natural reserves, and especially during the monsoons, which is when mosquitoes breed the most, it wouldn't hurt to carry a mosquito-repellent cream with you.
Many travellers I know (who went to Africa) do not use profylactic antimalarials (like Lariam) because of the harsh side effects. They have some medicine to take AFTER the get malaria, and usualy travel in dry season only. Moreover, I heard that you can use herbal tea from (I guess) Artemisia annua as a prevention!
If you hate to use chemical repellents like I do, you can use Citronella oil, but you have to apply it more often than chemical repellents.
I advise against taking anything. The side-effects can be harsh, in fact I wasn't able to enjoy my trip until I got rid of the medication. Furthermore, especially in India, you're traveling from city to city so the chances for a malaria mosquito finding you are really low. You're much more likely to be hit by a car, suffer from too much heat or get an intoxication by street fumes.
Just use the usual precautions, especially a repellent. Don't buy into anything anyone recommends, find out what reacts well with your own body. When you've found your repellent, you'll realize that the mosquitoes stay away ;).
I have lived in a town the middle of South India for years. There are hundreds of foreigners living in my town. There are also thousands visiting each year. I've never heard of anyone taking malaria pills. Nor have I heard of even a single case of Malaria in this area. This is just some personal experience.
Malaria is a serious and sometimes fatal disease transmitted by mosquitoes. The risks to health whilst travelling will vary between individuals and many issues need to be taken into account, e.g. activities abroad, length of stay and general health of the traveller. So it is recommended that you consult with your General Practitioner or Practice Nurse 6-8 weeks in advance of travel. They will assess your particular health risks before recommending vaccines and /or antimalarial tablets.
The risk is highest in north-eastern states including Assam and Orissa. It may be considered for certain groups who may be at higher risk e.g. longer stay in rural areas, visiting friends or relatives, those with medical conditions, immunosuppression or those without a spleen.
For further information about Malaria precautions and for full list of the highest risk area list, check the official NHS site (Fit for travel).
Please check the following map for further details for areas with high risk:
Please note that Mefloquine (anti-malarial drug) since its introduction, it has been directly linked to serious adverse effects, including depression, anxiety, panic attacks, confusion, hallucinations, bizarre dreams, nausea, vomiting, sores and homicidal and suicidal thoughts. Therefore Malarone has the fewest reported side effects and it's which is much more recommended in preventing and treating malaria.
- Malaria Travel Health Advice at Fit For Travel (NHS) including country specific malaria information and malaria maps.
- Malaria and Travelers at Centers for Disease Control and Prevention (CDC) to find out whether malaria is a problem in the country where you will be traveling.
- 'I regret not taking malaria pills' at Evening Standard