I have always been partial to White's. May have something to do with the fact that I started with a Whites DiPro 20 years ago.
Here's a few rules I live by:
I strongly recommend you review the laws concerning where you can and cannot hunt. Federal parks and civil war battle fields that are marked will result in the levying of serious fines and likely get everything with you confiscated.
In my time I have found roughly $65,000 worth of silver, gold and gem jewelry. I don't believe in using a "shovel". There are several models of diggers that are bladed on one side and have a saw on the opposite. Check Ebay for them. Using one of these with some practice will net you much better results. A clean cut hole is much easier to refill. When I leave a place after an all day hunt the only tell tale sign that I and mine have been there is a little loose dirt. Dare you to find the holes we dug.
Leave wherever you hunt in better shape than when you got there. We clean up loose trash and take all the "junk" metal we dig out of the site with us and deposit it in a trash can. You will be rewarded by compliments and return invitations.
Go with someone. Not only is it for safety, (heat stress, idiots, accidental self inflicted wounds), but you have bragging rights for the day for best find, oldest coin etc.
I'd recommend making a test bed for what ever it is you are hunting. In the case of coins mark an area in the ground, put a quarter, dime, nickel and penny at different depths flat and on edge and see how your machine reacts to them. Once you speak your machines language finds will come steadily. Note: small gold rings will come in the "pulltab/nickle" range. Don't descriminate these out as you will leave a lot of great finds behind for me to find! (on second thought....yes you should descriminate those things out...LOL!)
Good luck on your hunts! If you have any questions I'd be happy to help you. I warn you though.....once you make your first good find you will be hooked. It gets in your blood!