You really haven't told us much of what you want to do, so it is really hard to recommend something. The usual routes:
1) Keep a log of what was in there last time, and manually poll for changes. This is about the worst route.
2) Use launchd and a "KeepAlive" key for the watched path. This is probably the best route for a script... but depends on a number of things, and since you aren't sharing...
3) Use the fsevents api to watch the folder. This will get you great notifications, but requires callbacks, so is difficult to do in almost all scripting languages (technically possible in Python, but really difficult).
4) Use AppleScript "folder actions". I have never done this as they have a reputation of being flakey.