I agree with Vikana: only buy when you think it is headed up. Scaling in as a stock drops is a play for extremely large size institutional buyers who have to buy when there is supply. There is one exception for traders with iron discipline. Put on your standard position when you think it has bottomed or is at support, then if it drops to your stop loss point, double up. If it drops even a tiny bit more, exit everything. If it rallies to where you are b/e on the entire psoition, get out. Only use this in extremely liquid stocks or, ideally, the futures. The beauty of this is you are risking very little on the add but the position only has to retrace half what it lost for you to get a push.