The scenario it doesnt work would be the following-
Say you wanted to have a 100 share position in STP and the first buy price was 44.75, but you only bought 25 shares thinking you could get a better price, so you just buy 25.
Then the stock goes from 45 to 50 to 55..good for the 25 shares, but you MISSED the full position getting 100 shares, so you only realize a gain on the 25 shares since it didnt fall and you didnt buy more.
The scenario it stinks is when the stock doesnt drop and you only get a part of the position purchased.
When I get into a trade I look at the number of shares I want to purchase overall..so if that is 50 shares or 5000 shares, I know what I want in total, then I try to buy on weakness and see if I can build a position. Then I decide how I want to buy the shares, in 1/3 position or 1/2 or 1/4th or the WHOLE thing at once (rare that I do so) and I start buying.
Now with STP this is how I would have approached it-
CHART
STP has been a SELL based on technical indicators since Jan, but ESPECIALLY since Feb when it was hanging around the black line (black line is the 200 day moving average) and it hit the red line (the 20 day average) and it broke down through that 200 day moving average which would be considered technical support..look at the blue line (which is the stock trading price) and how it bumped against the black line for a full year..then in late Feb it crashed through the black line the 200 day support and failed..went lower..that is a technical failure and it was time to be OUT of the stock from a trading perspective.
Now notice that the 200 day moving average (the black line) is where the stock bounces to and fails to go through it..that is called resistance..and until it breaks that 200 day moving average and we start seeing the green and the red (the 50 and 20 day averages) start to slope UP, the stock is still in a down trend.
This is an important time for the stock technically, the moving averages are conflicting..one moving up, the other has been trending down, but if you get that green line to trend up and intersect with the red line and the stock moves through it and the 200 day, you could be in a very good trade.
Now if you were long the stock I would keep an eye on those technical indicators and my next buy would be if the stock hit that green indicator, the 50 day and bounced up off it..which means the 40-41 area..that would be my next buy point.
Look at how explosive it can be when a stock breaks above the moving averages-
DRYS
Its been good for 20 pts after that breakout..and I have been quite happy.
Ask questions, most of us are good at understanding this and are more than happy to help.