My personal strategy has so far been to buy little bits all the way down. At the equiv of USD 0.40 I'm buying bigger little bits (tenths of BTCs rather than hundredths) whenever the price nears a largish buy wall on polo. At USD 0.20 I will probably start buying even bigger little bits. If it goes as low as USD 0.10 (and nothing major has shown up to scare me off) I will probably start buying as heavy as I am comfortably able to.

Of course, I treat all of this like gambling and never play with anything I am not willing to lose. Also, I am not very smart. So please do not take my words as a recommendation to do or not do anything.