1. Build Probe #5.
2. Have the 4 probes to gather from different mineral patches.
3. Build up to probe #8.
4. Build a Pylon and a Gateway.
5. Build up to probe #10 and build an assimilator.
6. Get zealots and try to slow any terran attacks.
7. Build Probes non-stop.
8. Build a cybernetics.
9. Around the 13th probe build a second Gateway.
10. Build citadel of adun.
11. Build a templar archives.
After completeing this, send a pair of DTs into your opponents base to scout. If his base is undefended, pump out more DTs and go to town. Even if you fail to eliminate your opponent with this, you will still be able to stave off and early ground attacks with the DTs.
*Note: This is intended to be used against Protoss and Terran. It is less effective against Zerg due to the overlords chance of detecting your DTs.
Here is a video with some good DT harrasment: