The only real way is to remove the water from the air before it condenses. the gel or crystals will work but you really need a dehumidifier
I have 5 boys and live in Wales whichis very wet. I have been using a dehumidifier for over a year now and it really makes a difference. I found gel/crystals were a waste of money. if you have a problem .
I looked all over the place for one and found that
4air.co.uk
http://www.4air.co.uk/index.php/cPath/860395437_2500/cna me/Home%20%26%20Office
was the chaepest and the Ebac came direct from their factory with a 3 yr warranty.
You can get them from argos etc but I found 4 air was much much cheaper..
You can use the water collected for house plants , they love it or for the car radiator as it contains no chemicals.