When the price is suffering a slow movement, most traders want this opportunity to grab some coins since once it goes for a rally again, they have the advantage and benefits.
In general, it's all about your guts to face the risk after you buy coins in that given price.
It is simple when to buy bitcoins, just always remember the traders move. But at low price and sell it on high price.
Don't wait for the price to go up before you are going to buy because it can be worst thing to happen if you are going to buy bitcoins today.
We never know which is the low price to buy and high price to sell, its a pure luck based so if you have faith in bitcoin then you can buy at any price that you see.
Well you are going to know it because you are going to see the price on the exchange sites and you are the one going to decide if you think that the price is down then go buy bitcoins, but if you are uncertain because you think it is high. Then don't buy bitcoins at all.
You may check the price at yobit.net or preev.com