Here are some tips I've gathered (and mostly tested) that will help you build a good test garden for your detectors. Some of these I came up with myself, others were gathered from detecting sites... I'm sure I'm forgetting a few things, but this will help you get started if you want to have a good test garden!
Sweep your prospective spot while in all metal (no disc) to make sure there is NO iron present. Remove any that is present...if it's flakes, find another spot
Chart where you bury stuff with a map! (yep..unless you're super human, you'll forget years down the road)
When digging your hole for placing the test objects, check them CAREFULLY with a pinpointer to be sure there's no other metal present.
When you place your test objects, pour a little salt water on the object while it's in the the soil, prior to reburying. This will speed up the effect normally seen when objects have been buried a long time. Caution...the test won't be legit until the salt water dissipates after a few days.
Bury coins and objects at different angles if possible so you can learn how they sound
Bury some nuisance items as well, beaver tails, pull tabs, foil, etc.
Golf tees pressed to almost flush with the ground, or gold ball markers can make good visual indicators of where you have things buried.
...MOLES! Yep...they will change things! (air space between the coil and the target)
Test your garden on dry days and wet, wet days to see the difference in signals
Bury some coins adjacent to common iron objects (square nails, for example) This is a great way to test target separation and detector reset speeds
Just for the heck of it, bury a coin TOUCHING an old iron object (like a nail)...interesting, huh?
When you REALLY want to go crazy, bring in some different soil types and fill in a 2 foot x 2 foot spot...red, iron rich clay has a very humbling effect!
Be sure to bury a few coins that are barely TOO deep. You may eventually find a detector that will sniff them out!
