1. Look for rubber damage: Check your wiper blades for any tears, cracks, chunks of missing rubber, splits, or other signs of damage to the rubber part of the blade
2. Check the frame: Look at the frame of the wiper blade to see if there are any signs that it is bent or broken
3. Test the blades: Use a spray bottle or wiper fluid and run your wiper blades a few cycles to see if they are effectively clearing rain, snow, sleet, and other road elements. If they leave streaks, make squeaking noises, or chatter across your windshield, it's a sign that they need to be replaced
4. Check for grime: If you notice a consistent film of grime on your windshield, even after you’ve sprayed fluid to clean it off, it's a sign that your wiper blades are dirty and need to be replaced
5. Age and advanced wear: Wiper blades are exposed to the elements and wear down over time. If your wiper blades are more than six months old or have been used for more than 6,000 miles, it's time to replace them

Remember, it's important to replace your wiper blades regularly to ensure clear visibility and safe driving during bad weather conditions.