That's your three basic ingredients of gun school right there:
- Sunscreen. This is so you will not be cindered and start sprouting tumors on Day One from being out in the sun all day. Do not say to yourself things like "It's October. What do I need sunscreen for?" When you're standing out in his rays all day, Mr. Sun will burn you as happily in October as he will in July.
- Water. Lots of water. And drink that stuff. It's hard to learn stuff when you're lying flat on your back, everything's fuzzy around the edges, and everyone's voice sounds like it's echoing down a tunnel. Besides you really can't learn anything when all anybody says to you is "Are you okay? Hello? Quick! Call 911!"
- Ammo and mags. Lots and lots of ammo and mags. Check with the course requirements or contact the instructor for a recommended minimum. The more mags you bring the less time you'll spend loading, and you'll still spend enough time jamming rounds into mags that your thumb will be sore for a day or two afterward.
Ammunition and mag requirements vary from instructor to instructor, and by the type of class you're taking. At Louis Awerbuck's three-day carbine/pistol course, I burned up something like 450 rounds of carbine ammunition and maybe 200 for the pistol, whereas the 2-day Aim Fast Hit Fast course with Todd Green used up nearly every bit of a thousand rounds of .45ACP.
Magazine requirements are usually more vague, and will vary based on how much time you want to spend stuffing rounds in magazines. Todd helpfully suggests to bring enough magazines to AFHF to allow you to bring fifty rounds up to the firing line. On the other end of the spectrum, I've watched a guy taking Handgun I with only the two mags that came with his Walther PPS. It seems like literally every second he wasn't shooting, he was pulling loose rounds from his pockets and thumbing them into magazines; it's gotta be hard to listen to the instructor when you're doing that.