One of the most important items in my shop is a new roll away tool chest that acts as a mini office. It is used to store all the parts, paperwork and revised instructions having to do with the bug. Every screw, nut, material and accessory is checked in as if it was being stored in the cart. Should I decide to build another BugE after this one, the second one assembled would go quite a bit quicker since I'll have records to allow me to easily combine orders and compare supplier pricing!
I'm also revising the manual to be more complete and that takes quite a bit of time and effort to do right.
If you are going for a tool chest, don't bother with the cheap ones at Lowes. Get at least a Craftsman tool chest. If you get one, spend a bit more for ball bearing or "quiet glide" drawers. The price may be only be slightly more if you catch a sale (and there's always some sort of sale at Sears). In my opinion, not hearing the cheap drawer slider noise and the convenience of the rear lock bar is worth the extra bucks. Plus, they seem to be made better and have large casters that can go over most anything.
Currently, my system is to take a guess on the materials needed for each step. (parts are listed, but there is always SOMETHING missing, even if it's something like a paintbrush). Then, I keep all receipts and using a custom MS-Access database, I check items into the figurative tool box. Then, when I have enough materials for a step, I'll try to do it. Any additional items I put in, I record and check in just as if I bought the items beforehand.
At this point, entry is not too efficient since I'm not sure what's important to track and what's not. I'm recording everything I can, even alternate suppliers and possible substitutions if I see the item available elsewhere. The database is relational so it's very easy to add/drop features to it. I'll have more news on that later.
Establishing the database was made easier by modifying a template from MS-Access. Time to modify the database, I would estimate would be about 8 hours to get it right for my use. Fortunately, I'm not in too much of a hurry so I don't mind spending some time thinking about my needs, then modifying a database to record them.