Start by using Minelabs factory settings, and forget about tweaking the controls and buying expensive coils until you know what you're doing. Dig thousands and thousands of targets, trash and treasure, and try to id each and every one of them. Use the meter as a numerical reference for the target tone, because unless you have perfect pitch, there is no way to tell the pitch of a tone without a reference.
Listen for distinctive changes in the tone, that is, changes in pitch, timbre, and loudness, as you sweep over the target. Sniff at the target with the tip of your coil, and if your still not sure of the target, approach it from another direction. Sounds complicated, but it actually takes only a few seconds.
Some newbies never get the hang of it because they give up trying, but I think it takes time for your brain to develop a "tone memory" that is big enough for accurate pattern recognition. Like hearing someone's voice on the telephone, you have to know who it is before you recognize them. It's hard to explain, but once you get the hang of it, no microprocessor based target id system can come close.
I hope you get what I'm saying, it's kind of like a gestalt, and after a time, target id becomes second nature. But there are no absolutes, so it is a continuous learning process. As time goes along, your skills just get better and better.
But most important of all is fod's treasure hunting theorem: "If you want to find a valuable treasure, you gotta have good hunting skills, dig lots of targets, and you gotta be very, very lucky."
I hate to be the one to break the news, but there is a lot more trash out there than treasure.
That's it.
Good Luck and Good Hunting
fod