Pullups can be pretty intense, but with any intense exercise it also means they bring great results. The key to perfecting your pullups is great form and modifications. If you're a beginner you should modify for your fitness level. If you're at an advanced level of fitness you can use modifications to make them more difficult.
When completing a pullup it's important to have good form to prevent injury. Use a pullup bar you can reach standing flat on the ground. You can place your hands over or under on the pullup bar, depending on the muscles you want to work, but make sure they are balanced well. This means equally spaced apart and equal distances from the ends of the bar. Hang from the bar with your knees bent and feet behind you. Pull up until your chin is just above the bar and slowly lower yourself down. This is a body weight exercise, so your own body weight and gravity provide the resistance.
Modifications for Beginners
If you're a beginner in your fitness routine or to pullups you can use a modified pullup until you build more strength in your upper body. Find a pullup bar at a comfortable height, this will help you modify the pullup safely. Work with a trainer, spotter or use a sturdy bench and do pullups with a slight support. If working with another person, have them hold onto your feet and use your feet to push yourself up as your upper body pulls you up. This provides leverage and stability.
Modifications for Advanced Fitness Levels
If you're advanced in your fitness level modify your pullups by adding weights to your ankles or a weight belt around your waist. You can also find a high pullup bar you have to jump to get on. Also, consider using ladders to strength your upper body and your coordination. Ask your trainer or gym owner about the ladder.