Ok, before we go any further here, nobody's mentioned the one "must have" item:
Gasoline is considerably easier to ignite, often with considerably more dangerous consequences, than glow fuel. Please have a suitable fire extinguisher on hand whenever working with gas-fueld RC engines.
And please actually have it on hand...not just 'somewhere in the trailer/truck/car", or "forgot it back in the shop". And please actually check it regularly, to make sure it's charged and ready to go.
I know, I know...I'm being the stick in the mud safety nazi here...but this is one of those things that lack of attention to can cause HUGE heartache for a GREATMANY people (like...an entire RC club), and it's so simple and inexpensive to take care of.
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Beyond that *heh*
I prefer to have 2 fuel cans. One small one with my fuel pump on it, easy to carry around the pits/flight line, and then a larger one kept in the trailer with my "fuel supply". That's just preference though, obviously so long as the fuel pump is gas ready, then whatever works for you works for you.
I find myself, after a few years of doing gassers, always carrying a quart of preferred oil with me...since, inevitably, if you don't, you'll run out of fuel, and while there's a handy gas station just up the road...they don't have BrandX 2-stroke oil! So, toss a quart or so somewhere in the vehicle just in case.
Also, I highly suggest using a sharpie to LABEL your fuel cans. I can't count the number of times I've not been sure if that can in the shop had the "airplane gas", with the expensive oil at the perfect ratio, or the "trimmer gas" with the cheap oil at whatever ratio looked good, or the lawnmower gas with no oil! Labeling the cans "Plane Fuel : 93 Octane 32:1" or whatever solved that problem.
Finally, along the same lines as what ndb8fxe said, gas fumes are more dangerous than glow/nitro for several reasons. So, whatever vehicle you're carrying planes in, do give some consideration to proper ventilation, or plugging exhaust pipes or capping carbs, etc. Obviously, this will all depend on the nature of your specific situation, but do at least keep it in mind and give the issue due attention.