What strategy you use to trade bitcoin?
Simple: Buy low, sell high.
Agreed but we don't know what is high and low in bitcoin, as price is constantly moving up and down, so if you are satisfied with price then you can buy and sell when you are making some profits from it.
High and low is always subjective, and it is basically whatever you think will be high or low within the Bitcoin economy. A low value of Bitcoin is relatively obvious, while a high value of Bitcoin is any point where Bitcoin is valued at more than what you bought it for, and what you're willing to sell it at. There is no definitive number for any of this, and a lot of it is very subjective.