Post job interview help?

I had my first job interview ever last monday after applying to about 30 different places. Obviously, it's been pretty hard to find a job as a high schooler with no work experience. This particular interview was for a cashier positions at a hardware store. I interviewed with the manager and it went great! He seemed to really like me and basically said that I was a great fit for the job and everything. I left feeling like I had gotten the job for sure but he did indicate that I was the first person to interview for the job and that it would take a week or two to make a decision. Basically, he said that I could possible hear back by last friday but at the latest by the end of this week but it's already thursday. I'm concerned that they will never call me. Should I call them today or tomorrow or how long should I wait? Also, what should I say and what time of day should I call. I've never done this before and really need advice!