Having the proper equipment in your range bag is critical to having a successful trip. Here is a quick checklist and some things you may not think about.
Ammo and Guns:
Obviously, if we intend to shoot our guns, we need guns and ammo. Make it a point to check that each firearm has the corresponding ammo. make sure you also have more than the ammo you intend to shoot as well. If you end up working a drill repeatedly, you will be happy you brought extra.
Mags:
Bringing enough magazines is another critical point. If you bring only a few, you will be constantly reloading those mags and taking away from your range time. Loading the magazines the night before a range trip can also increase your shooting time. If you have one, use a loading assist device such as the UpLula magloader to make loading magazines faster and easier on your thumbs.
Maintenance:
Your range bag should have a dedicated bottle of lubricant, as well as tools to disassemble your firearms. If your gun has troubles, you should have the ability to fix it on the range and get your session back on track. In addition to the normal maintenance tools, having a brass or aluminum rod to clear a bullet from the bore is also a good tool to have. Though uncommon, a squib load can ruin your day if you can't clear it.
Protective Gear:
Eye and ear protection should be taken seriously. Once damaged, it is rare that sight or hearing returns. Invest in quality eye protection that has a ballistic rating for impact. Make sure that you bring a good set of ear protection as well. Active hearing protection is also very nice to have if you have other shooters with you, making communication easier. In addition to eye and ear protection, don't forget sunscreen, lip balm and cover garments such as hats, SPF shirts and other items to protect your skin.
Sanitation:
Finally, something that people often forget is that we are putting lead particles on our hands and in the air. Having some baby wipes or D-Lead wipes means that you will not have to be concerned about lead poisoning from hand contact.
Of course anything else you can think that would make your experience more enjoyable should definitely come with you!