Memorize perfect squares
Estimate between the nearest perfect squares
Use prime factorization for perfect-square numbers
Pair factors under the radical and simplify
Use long division square root method
Use the Babylonian method
Use Newton’s method
Use approximation with nearby decimals
Use fraction benchmarks like 1, 1.5, 2, 2.5, 3
Check by squaring your estimate
Refine the estimate if needed