If you have access to a pool and very slowly submerge (feet, knees, chest, neck) you may be able to trace bubbles. If not, you should at least get an idea of location when you start to feel wet. Wearing thin undergarments with light colors will aid in seeing water spots.
As mentioned above, turning the suit inside can be helpful as well. I have found a leak this way in the past by shining a flashlight in relative darkness on the inside (outside) of the suit.
Do also check your seals carefully. I couldn't find a leak in another suit and the manufacturer tried to duplicate the leak for 3 weeks before finally finding a tiny pinhole in the neck seal.