When cruising at high altitude in cloud or at night (30,000 ft upwards) set the Gain control from the Auto position to Max gain position. This gives extra beam power and allows better pick-up of tops of storms which normally do not have much moisture in the anvils or tops. Works a treat in the tropics which have huge tops.
The Collins WXR-700X Pilots Guide is full of good information and if you play your cards right any Rockwell-Collins agency will give you the book free.
Also read a fine book called Airborne Weather Radar - A User's Guide, by James C. Carr. Order it from USA phone 1-800-862-6657. It is around $40 USD and nwell worth it.