To increase speed you need to do interval training. You can google or yahoo interval training on a bicycle for more information. Interval training slowly and safely helps you develop speed and leg strength. What's this means is that you pick a distance, say 20 miles and within that distance you will be riding moderately with a comfortable cadence of 80 and then for a short distance (to be increase over time) you will step up the cadence to 100 - 120 without changing the pedal gearing. As your speed improves the gearing goes up and strength develops, etc. There is a whole science to this and lots of books written on the subject. To improve pace up a hill, you would use the same method. Don't be afraid to stand and power up short hills. High cadence and lower gearing works best up long hills.

Also learn to ride in a paceline (again the google thing). A definitely plus on long rides or in a headwind. Also use a heart rate monitor. This way you know if your are stepping up your effort. You need to know your min/max heart rate. You should alwys ride toward the lower equation but during interval training, push your heart rate up towards the high end, back off and see how quickly your heart rate returns to its normal pace. You can measure improvement when the time difference is very small.