This is a great thread with great potential for sharing knowledge, where to start!
Scalping is a fantastic daytrading technique (I am a private equities fund manager) and have colleagues who are scalpers (and very successful ones too!).
They all have several qualities in common:
1) They have lightning quick reflexes
2) They are single
3) They like playing video games
4) They have nerves of steel.
As far as their actual techniques go, they are all different.
I believe that a general rule of thumb for successful daytrading it to keep your profit targets high (infinite if possible!) and your downside risk minimal.
This also means to make sure your holdings are quick. This is a double -edge sword though as Larry Williams has taught us that profits are a function of time, ie, the longer you hold, the greater the opportunity for returns.
Hope this helps,
Good luck in your trading education!
-HedgefundJim