1993 Ford F-150 Electrical Issue?

Last fall I tried to start my truck, but when I turned the key there was no power at all, no radio, dash lights, door chime etc. I assumed that it was a dead battery, and then just left it where it was as I had access to other transport. Today I jumped in and tried to start it and it turned on and started normally, no indications of a power problem at all. I turned it off, and when I tried to start it again the same problem came back, nothing worked. I took out the key, put it back in and for a second or two there was full power, I could hear the fuel pumps starting up, but then it went dead again. Now I can't get any response, I've tried moving the steering wheel around, jiggling the wiring harness and yelling obscenities. I assume I have a bad connection somewhere, I was just wondering how to narrow my search/how I could fix this?