The Golden Rule of frequency selection says to use the lowest frequency that will produce a traceable signal over the distance you need to cover. Your best strategy is to choose a frequency based on the resistance of your circuit and what you want to do.

• If you have a good circuit and you want to go very long distances use a low frequency.
• If you have a good circuit and do not need to travel as far then start with a medium frequency like 8kHz. Usually a good frequency range to start with in most circumstances.
• Because of the higher risk of bleed over and their limited range higher frequencies are best used on poor circuits or when lower frequencies have previously failed.
Very high frequencies should be used as a last resort or if you want to energize as much area as you can just to see if anything is there.