The 1-2-3 continuation buy is a common chart pattern.  There are many sources of information for trading this pattern, including our friends at Pristine.com.  A typcial interpretation is listed below.

Setup:  Bar 1 is a tall green bar.  Bar 2 is much smaller.  Bars 1 and 2 form a mini-double-top.

Action:  Buy as soon as the price crosses the top of bars 1 and 2.  Place a stop loss at the bottom of bar 2.