Hunting in A/M or Disc mode you'll have to decide which you like better. A rule of thumb is if your in a high trash area you'll want to disc out the trash, if your somewhere with few targets A/M might be the way to go, or you may want to cherry pick or........ Like I said you'll have to decide.
Again what you notch out is up to you depending what your looking for. I notch out everything but nickels when hunting parks just so I avoid trash. On an old home site I start out digging everything above iron and go from there. Out in the woods I dig it all because when you start to find iron you found human activity.
Starting out go by VDI and as you learn the machine you will learn it's sounds. The F4 makes very unmistakable sounds over different targets. The shape of the sounds are a wealth of information, before long you want even look at the VDI only as a back up to your ears.
The F4 has a short learning curve but never stops amazing. So dig dig dig.