1. Different Exercises. The best way to fix a boring workout is to switch exercises. For example, if you've been doing the chest press with the bar, switch to dumbbells. If you're already doing a lot of dumbbell exercises, start doing some of them on a bar or cable machine. After you do the same exercises week after week, you're eventually going to get bored. It's like listening to the same song everyday, eventually you're going to get bored if you don't change the track.
2. Workout Buddy. If you workout alone, try finding a workout buddy. Not only will this give you someone to talk to, an exercise partner can inject fresh ideas and knowledge into your routine. They'll get you to try new exercises and methods you might have never even heard about which is an easy cure for boredom.
3. Different Splits. Try switching up your splits. If you're following a chest & triceps/back & biceps workout, flip it around. Start working out your chest and biceps together and back and triceps together. You can get really creative with this. Give arms their own day. Workout shoulders with legs. Try doing chest all by itself. The combinations can go on for a long time.
4. Keep a Workout Log. Try keeping a workout log. Write down the order of every exercise, weight you do on each set and amount of repetitions you complete. It can be very motivating to use it during every workout and see how the numbers keep going up and you keep getting stronger.
5. Order of Exercises. Try switching the order of your exercises around. It might get boring to keep doing squats first on leg day so why not try doing the leg press first, then deadlifts, then squats. This way you'll be able to improve on an exercise you've been doing last in your rotation.
Honorable Mention. Rest. If all of these suggestions fail, don't be afraid to take a week off. Sometimes, boredom with your routine can be a signal that your body needs a little time off. Remember, you grow when you rest and if you're constantly hammering away at your muscles, you'll never see any improvement. Sometimes a week of rest will allow you to start off fresh and erase away any boredom you may have had.