What Criteria Do Miners/validators Use to Select Transactions from the Mempool?

Miners or validators primarily select transactions based on the offered fee per unit of gas (gas price or priority fee). Higher fees mean a higher immediate reward, so they are prioritized.

Other secondary criteria can include the transaction's age (to prevent starvation), the total gas limit, and, increasingly, considerations for Maximal Extractable Value (MEV) to optimize the block's total value.