http://www.diydata.com/problem/condensation/condensation.php
Mostly ventilation and keeping (letting out) the steam down
A dehumidifier may help to begin with
An RH meter from a garden centre can had for about £5
Most of your damp will be generated inside the house by normal living - a leaking gutter may be a cause on an external wall but it hasn't been raining much lately.
Peccavi
February 2010