A good tip is to drink lots of water...all the time. The tubes can get blocked if the mucus inside them is sticky and slow to move. It really needs to drain effecively and if your body is well hydrated then it should. 3 litres a day each should be enough - sipped gradually throughout the day (and it is good for you anyway) and once your body gets used to it and begins to retain it you'll stop having to p so often!