Secret #1 - Minelab Explorer or E-Trac. I have never found as much silver as I have with Minelab machines. It's unreal what I've literally walked over for years with other machines. If you look at the serious hunters who find tons of old coins in hunted out parks 9 times out of 10 they have Explorers. In my first 15 or so years of detecting I found 200 silver coins. In the past two years with Minelab machines I have found 150, from the SAME sites I was hitting years ago.
Secret #2 - Go slow, be patient, take a deep breath, keep your overlap tight and listen for every beep.
Secret #3 - Dig anything non-iron that registers deep on the depth meter. Around here a pulltab
Secret #4 - Go detecting... a lot. Some weeks when the weather is ideal in the spring, I will be out detecting for 20-30 hours a week. My average hunt is 3 hours.
Secret #5 - Give up on a site. If you're not finding anything and getting frustrated or tired you're not going to do your best. Know when to take a break or move on to the next site. Many days I will hit 3-4 sites before I find one that I'll stay at. You can always go back another day.
Secret #6 - Research. Go to the library and read histories of the area, find old photos, look at Google aerial maps and the old Sanborn maps. Have a visual in your mind of what the place looked like 50 years ago.
Secret #7 - Try anywhere and everywhere. Even if your intuition tells you there was nothing there or should be nothing there, get over it. It doesn't take much time to check out a site and see if it's worthy of more time. I roam until I find a hotspot. Many of the parks around here have been bulldozed and backfilled so finding unmanipulated ground can be tough. In the old days, I used to work the edges of sites, but others have caught on to that. Under and around bushes too - those bushes weren't there 20 years ago, and they sure as heck weren't that big.
Secret #8 - Once you have a hotspot, rework it at 90 and 45 degree angles.
Secret #9 - Cherrypick. I don't dig shallow zinc cents in parks. I might miss gold, but I'd rather have old coins anyway. I also tend not to dig pulltab signals from 2" to 4". This seems to be where the carpet of tabs falls off. I dig tabs, but they are 4" or more in depth.
Secret #10 - Retrieval - Sunray Inline Probe and good digging tools - fast recoveries mean you can cover more ground. I watched one guy chasing a signal around a hole for almost 10 minutes. I would have had it in 30 seconds. That gives me 9.5 minutes more detecting time.
Secret #11 - Positive attitude and confidence in your machine and skills. If you know you can find it, you will. If you doubt yourself or your machine, you'll probably fail.