Not using a pasta shape that allows for the dressing to really stick to it. 2. Overcooking or undercooking the pasta. Not enough cooking and you've got pasta that is hard to eat. Too much cooking and you've got a gummy macaroni salad. 3. Not seasoning the pasta enough. Salting the water you cook the pasta in as well as seasoning the salad right before you serve it helps with this. 4. Stirring the macaroni salad instead of simply tossing it. Stirring it will make for a gummy mess. 5. Not giving it enough time to chill before you serve. This dish is make ahead for a reason. The time in the fridge makes it magic.