just a comment before you start with interval training or doing hill repeats. Make sure your have a good base. Meaning you can comfortably ride a 20 mile ride or even do a 50 mile easy ride at a reasonable pace. If you are older and have been sedentary, make sure you get a cardio check first with a doctor.

If you don't have the base conditioning, doing intervals or hill repeats can hurt you. And always listen to your body for aches and pains. Some are good some are REALLY BAD and you have to learn to differentiate them.

Lastly, unfortunately there is no magic bullet to make you go faster. Just hard work and training.

Others have made great suggestions.