How to use a trigger (SMA/EMA etc)

Hi. I have been buy-n-hold investor. I want to use a small amount using SMA/EMA as triggers for buy and sell. I noticed that when such a signal happens, it moves across the trigger line many times during the day or the week. Is it typically a common knowledge that you can wait until the end of day for the crossing to be still valid before they buy or accordingly? Please help me understand. I highly doubt that triggers that it crossed more than once a day should actually cause multiple buys and sells on the same day.