The only way you can increase speed is to practice practice practice.
There really is not easy way - however there are some good and bad ways.
Some people try to learn fast passages by getting the very basics of the fingering and then repeating it as fast as possible over and over. Now this may work but I have found that generally this will not help.
The way I do it is to start very slowly and get every note perfect and I mean *every* note perfect. Then slowly, day by day, build it up. If you have a metronome to work with then this will help monitor your progress.Just go up one BPM every day and you will get there.
The great thing about doing this is, once you have it up to speed, it will sound perfect which I think is what we all want.
And the lessons that you learn in doing this, quite monotonous task is, the next fast piece that you want to learn you will get there much faster and find it much easier as you are training your fingers, and your brain to play at speed.