Camera, check. Battery, check. AC power, check. Recording media, check. For the final thing, read on.
Packing camera bags is simple on the surface, so let's dig deeper. The camera is necessary for obvious reasons, but its fit in a camera bag isn't always clear when you get your bag for the first time. As with other areas in life it's good to start filling space with what is most complicated, and that means the camera. Though the shape of your camera may not be as awkward as a sectional sofa or a garlic masher, the camera should be the biggest thing in the bag and will need to be removed the most often. Protect as many points of the camera as possible and resist movement side to side as well as up and down. You're looking for the medium in which the camera is framed enough to easily remove but not shift around in transit. If you have soft inserts, these can generally be customized. Having an inner strap or catching mechanism can help keep the camera in place in the event of an open bag accident. Be sure to check the camera for a lens cap and remove the other essentials, such as a battery, AC power cords, and media cards.
The battery and AC power should be givens, but we still manage to forget them from time to time. Without power you will capture no images. Call it a pet peeve, but batteries should be fully charged whenever possible and spares even more so. Except for DSLRs, you'll often have an AC adapter to power your camera indefinitely without taxing a battery. Having space in the camera bag for a neatly wound cord can be tricky, but very much worth it and easy if you use any sort of cable tie.
So we come to the penultimate camera bag item, recording media. Play the matching game and be sure that you have a way to record your footage, sometimes cards need to be configured to cameras, and even tapes need to be unlocked (if you've ever found a good time to lock your card, please tell us, those little tabs only seem to be nuisances). You don't want to run out to a shoot and find your media slot empty - an inefficient trip resulting from an absent and very small item. Spares here deserve bonus points if they last as long as your battery.
Confidence. Being confident that the camera you put in the bag has captured great shots and will be protected, is necessary to videography. You take all your takes and put them in one camera bag, if you've got a long ways to travel, this volatile time is where your camera bag needs to provide the most protection. Until you can safely remove the media and create backups of your work, the bag is your safeguard. OK, so confidence shouldn't be contained within the bag, but that's what you'll need from it.
All else is gravy, though the tripod comes in close contention, it generally deserves its own bag.
Jackson Wong is an associate editor for Videomaker