Maffic

Hey,
The other day I was driving when my voltage started to drop. I got home o.k. but the voltmeter on the dash was reading only 9-10 volts. I checked the alternator at Kragen today and it came back fine. I'm thinking bad positive connections caused this, but I checked all the ring terminals (alternator post, batt terminal, fuse box) as well as the fuse and everything checks out. Now i don;t have a multimeter yet so All this was visually done, but the terminals still looked fine. Some were even shiny. Now what? If I went and got a meter, is there any way I could determine where the problem is so I don;t have to start opening up wires indiscriminately hoping to find something? Thanks much, and yes I searched.