Originally Posted by caloso

Here is the simple answer: to ride faster you must ride faster.

A simple, time-honored, and effective way to do this is to start riding with someone who is just a bit stronger than you. A variation of this is to find a group that you struggle to not get dropped.

If you don't like riding with others, you can do intervals. Essentially, instead of riding your whole ride at one speed, you are going to break it up into shorter time segments (intervals), ride those harder than you could for the entire distance, rest and recover, and then repeat. You will get faster.