What is the most common or some problems to look into when it comes to the transmission slipping. the car is a 3.1 V6 Pontiac Grand Am. i have some ideas but dont want to go out and replace something that don't need to be replaced.

The first and foremost ( and cheapest) problem is inadequate fluid level. To check your fluid level properly,l run the car for a bit until it is at normal operating temperature, and check it while the vehicle is running. Failure to do this will result in an inaccurate reading. If the dipstick indicates you need to add fluid, do this with the engine running. Add a little bit of fluid at a time, then cycle through all the gears (P,R,N, D), leaving it in each gear for a few seconds before moving on to the next. Repeat this process until you the dipstick indicates sufficient fluid. Be careful not to overfill, as grossly overfilling the transmission can result in damage. If your problem is not insufficient fluid, the next most likely cause is poor fluid condition, requiring a good drain and fill to remedy. Take a look at the fluid on the dipstick. Good fluid should be bright red. If it is brownish, or appears thin, you need to change it. Accomplish this by draining the old fluid, usually requiring you to drop the transmission pan, and change the transmission fluid filter located inside the oil pan. Then refill according to the process above. If the problem persists, you progress into possible pad shift solenoids, or possible deteriorating bands, the latter of which will require a transmission rebuild or a new transmission. Hope this helps out, and hope your problems don't turn out to be too severe. Good luck and have a great day!