Firstly, you must come up with a theme to design your character by. Building a human is no fun, theres plenty of those around. Animals would be exciting, but I'm not skilled enough to make it life-like. . .so I picked something inanimate. Being an electronics junky, I followed down that train of thought and came eventually to something that I hadn't seen in quite some time. . .a large older model Motorola phone. You know the one I'm talking about, the "Zach Morris Phone". Now I picked something electronic because I'm passionate about them, so you should pick something you like in order to enjoy the project the most that you can.
Hopefully you've come up with a character, so lets move on. . .
Step 1: Scrounging
In my line of work (school), our projects only exist thanks to those that throw things away. For this project the structure, body, and details were all created with cardboard, as are most of my projects. Now stores sell boxes, which is really terrible cardboard (I'm an expert), plus it's expensive. Art stores sell flat sheets of cardboard, but once again, it's expensive.
My favorite place to go is the appliance store. They have so graciously separated the cardboard from the rest of the garbage (mine all have separate dumpsters) so it is clean, free, and thanks to refrigerators, very large. They also have some cool types of cardboard, such as compressed and layered columns, angles, and rolls to provide structure for the appliance boxes, and also thicker sheets up to 1" usually. That being said, if your appliance store chains their dumpster like some do, you could always go into any big box store and ask for boxes because they too separate them. Stores that carry garbage pails and plastic totes usually have the largest boxes. Remember, ask nicely and say thank you.
I guess we got a little off track from the actual Instructable, but its its useful info so you can let it slide, right? Thanks.
Anyway, back to scrounging. Luckily between my roommates and myself plenty of cardboard and paint for the numbers could be had, but no gray paint for the body was available. A trip to your local paint store can solve that problem and rather cheaply if you go right to the mixed-wrong paint shelf. Some of the colors are bizarre but you can usually find something close to what you were looking for at a nice bargain price.
I've just realized I like to ramble, so on to the next step and I promise it'll be brief.