Originally Posted by travelerman

Find a group to ride with, preferably not a seasoned bunch of 20 mph+ bike jockeys.
I was going along happily at a 15 mph average, and the bit of competition provided by riding with others, plus the occasional draft line on the longer flats, helped me to raise my average almost unconsciously.

Another tactic that helped me earlier in riding and training was including a nice flat and straight section near the end of a longer ride to increase speed and endurance, and work past the bonk barrier.

Others will promote the concept of intervals, and there is every reason and evidence from all fitness disciplines that shows the value of shaking up an otherwise steady activity with segments of increased effort to your anaerobic threshold. This is essentially what you would be doing with the first two suggestions, if you feel too silly just cutting loose and pedaling like mad while riding on your own.

It takes time to build or re- build fitness, especially if you belong in the age group for whom this section of the forum is intended. I had a helluva time just getting back to rides of over thirty miles when I got back into it, and I have discovered that what they say about the difficulty of building new muscle mass when you hit middle age is all too true.

One other thing to observe - make sure you are consuming recovery food and drink after you put in a reasonable effort. Even when I ride for only ten - fifteen miles, I drink 8-oz chocolate milk after - for longer rides, I will drink a whey protein shake, and eat an apple or banana.