For leptospirosis, basically the rule is to avoid soaking in dirty water like flood. I know a lot of places in Manila gets drowned whenever it's rainy season and as much as we don't want to get wet, we do because we don't have a choice. So for that, let's just make sure that we wash off thoroughly with water and soap. Also, wearing boots and overalls would help IF you really can't afford to confine yourself at home. You may read the symptoms and treatment of leptospirosis at the latter part of this article: http://www.rappler.com/nation/41061-metro-manila-leptospirosis-philippines While for dengue, agreed with the above comment but to give other tips like: help secure your home mosquito-free by putting screens on your windows and adding some mosquito traps which you can buy from malls; wear long sleeves, long pants and socks if you need to leave the house and you think your destination might be mosquito-infested area.
Children should always wear mosquito repellents, with reapplication every couple of hours. Making sure that the house and the areas around it doesn't have stagnant waters in which mosquitos breed.