4. It's all in the timing

The single most important skill in Flappy Bird is timing your taps. The game is entirely about getting the bird through the pipes without touching any part of them. That means you have to learn to keep it as level as possible. Since the bird is always coming up or going down, the trick is to time your taps so that the amplitude of those peaks and dips are as short as possible — short enough to fit through the pipes. Tap quickly, tap regularly.
The next trick is to learn to recover to that rhythm quickly after you rise or fall to the right height for the pipe. You'll need to tap or double-tap up, or pause down, then get stable again really fast. If you're a natural, curse you. If not, you're going to have to practice. A lot.