If your pH is staying stable or rising very slowly then your TA is fine. If you pH is rising too fast and you have a big acid demand then your TA is too high. This is if you are using unstabilized chlorine like bleach.
If you are using trichlor or other acidic sanitizers or using non chlorine shoch, which is also acidic,then make sure your TA is at least 100 ppm to counteract the acidity these chemicals are constantly adding. the higher TA will cause the pH to rise faster and offset the pH drop these chemical cause. Make sure the TA does not drop too low in this case or your pH will start to bounce and can crash.
Where you put your TA depends on what you are putting in the pool. As a rule of thumb (and based on NSPI/APSP guidelines):
Keep it low (below 100) if you are primarily using sodium hypochlorite, calcium hypochlorite, lithium hypochlorite, or a SWG.
Keep it high (above 100) if you are using trichlor, dichlor, bromine, chlorine gas, or MPS (non chlorine shock) on a regular basis.
