ORIGINAL: carrellh
This part I've heard about, but have not gotten there yet: After a few years of lugging your entire workshop around, you'll scale back to the bare essentials to get the plane fueled and started; possibly a spare prop or glow plug.
My brother and I fly together. Our club uses a field that is 45 miles from my home, and almost that far for my brother. We're still at the place of carrying lots of spare hardware and tools for moderate ability to do repairs at the field.
When I stared flying I was like most beginner pilots, I had a flight box that was stuffed to the gills with tools and parts. After a couple of years of lugging that monster out to the flight line I came to the conclusion that I needed to do something different. So here's what I did. First I split up what I take to the field into repair tools that can stay in my truck and things I needed on the flightline for flying. Then I decided that I needed to take less tools to the field. Some guys seem to carry every tool to the field with them (heck, I think some of them could fabricate a new engine from scratch with all the tools they carry

), but I decided to not do that any longer. I only take the basics to the field with me any more. Enough to do simple repairs like tightening loose items, changing props, repairing holes in the covering, etc... But for bigger repairs I simply take the plane home. I hate doing field repairs because they are pain to do and most of the time you can do more damage than good doing a field repair. I can't even count how many times I've watched guys rush through a repair at the field only to have it come loose in flight and the plane crash, whereas if they had gone home they could have done the repair right and would still have their plane. So for me, only simple repairs at the field. This usually doesn't ground me because I always take at least 2 planes to the field, usually it's more like 3 or 4 planes.
Anyway, back to my flight box. Since I was tired of lugging a flight box to the flight line I decided to find something with wheels on it so I wouldn't have to carry it. I found a tool box at Lowe's that was perfect for me (see pictures). In the bottom of the box is a 12v lawn mower battery (needed for starting larger engines, 140+ size) and 2 one gallon containers for fuel (one 15% for the majority of my engines and one 25% for my YS). In the top tray I keep tie down ropes, my electric starter, my field charger, glow driver, overflow tank to catch fuel when filling, and my fuel pump. That's all that goes out to the flight line/pits with me, that's all I need there. I've had this box for about 4 years now I totally love it. I have two 12v taps on it (one for my starter and one for my field charger). I do have the power panel on there but I never use it and will probably leave it off if I get another box later on. The best thing about this box was that I didn't have to spend a lot of time "building" it. I had it ready to go with about 20 minutes worth of work.
I know that everybody has their own way of doing things and I would never think of knocking somebody for how they do their equipment, but instead I bring this up to show that there are alternatives. Many beginners (myself included) think that they need a huge flight box with every tool they own when they go to the field. I have found that KISS (keep it simple silly) works a lot better for me. I'm pointing this out so that beginners out there can see that there are other ways of doing things.
Edit: Forgot the picture of my box
Ken