This is the most common illness among tourists. It doesn't matter what destination you are heading, diarrhoea infections are also common in Bali. Also be careful when swimming in the sea. Best thing to do is take a mosquito net with you. I had a small anti-mosquito evaporator with me, but in certain areas like Lovina, it didn't help a lot.
Some people try to take B-vitamins.
When sweating the vitamins will make you smell like hell for these insects. Once the night is falling, you might think of wearing long clothes like light pants and a very light trouser. Visa and Mastercard are accepted in most of the hotels. However, in the smaller less tourist areas you might take cash money with you. If you are planning an adventurous trip, you'll need cash.