What is the correct procedure if fuel imbalance is detected before spins?

When a fuel imbalance is detected before executing spins, ensuring that the imbalance is less than 50 lbs is critical for safe operations. A fuel imbalance can affect the aircraft's handling characteristics and performance, particularly during maneuvers such as spins, which place additional stress on the airframe. Keeping the fuel imbalance within this limit helps maintain the aircraft's balance and control, thus reducing the risk during flight operations.

Checking the gauges is an important step, but it's more about monitoring the situation rather than taking action to ensure safety before performing spins. Making a routine call to ATC involves communication that is typically unrelated to immediate safety concerns about fuel imbalance. Performing an emergency landing is an extreme measure that may not be warranted in cases where the imbalance is minimal and manageable; thus, simply ensuring it is within the safe threshold is the most appropriate procedure in this context.