How much should a transaction fee be?

When it comes to cryptocurrency transactions, one of the most common questions is: "How much should a transaction fee be?" This is a crucial consideration, as the fee you pay can impact the speed and success of your transaction. So, what factors should you take into account when determining the appropriate fee? Is there a standard amount that all users should follow, or does it vary depending on the specific circumstances of each transaction? And how can you ensure that you're paying a fair and reasonable fee, without overpaying or risking the failure of your transaction?