In my first year, a vet told me to blow the whistle like you were in an arena with 20K screaming fans....I wasn't putting enough air in it and it wasn't sounding confident....
Pretty much what KS said....
On the subs...if you need to get their attention at the table if you are opposite floor, I will give a couple of quick chirps and wave them in.
Make strong calls and "sell them" with good mechanics....After you get your first call, you'll settle in...
Last bit of advice I can give you is just slow down....the game isn't going anywhere without you....no need to hurry on reporting....when you do blow the whistle, repeat the offender's # and the offended to yourself as you walk to the table so you remember who the call is on and who your potential shooter is....Nothing like heading to the table and having a brain fart on the player who committed the foul....Not that I've ever had that happen!
