Honestly I think that Pontiac made the overflow reservoir too small. I have to add antifreeze to my GF's Grand Am once every couple months. If its a consistent problem where you're having to add antifreeze daily/weekly the car may be running too hot, and should probably be looked at by a mechanic.
heater core has a leak replace heater core
The overflow tank is either cracked or its overheating and leaking from the cap
If its the little "elbow" that comes out of the fire wall on the engine side then it means the heatercore is leaking. This is a drain hose for the ac and if the heater core leaks it drains thru this tube
from your overflow valve
You may have a bad radiator cap.
check your water pump. I had the same problems last winter and that was the problem. a pretty easy fix. a bit bothersome but with the right tools anything is possible.
An overflow pipe on a (toilet cistern?) will leak if the rubber disc in the ballcock slide valve needs to be replaced.
Because your transmission has a seal that is leaking.
bad radiator cap
Yes. You will know if your car starts leaking it massively. And it will overflow.
woot woot
It could be the coolant overflow tank that is leaking.