Buy Bitcoin at low price,wait some time,and sell high.
The secret is patience.
It is easy to say than to do using this method. As small fish, we do not know the intention of big whales who can manipulate the price easily. They determine the direction of the price. When we buy, the price can drop further, and do not rise for long time. When we sell, the price can go up for some time without dropping below our selling price.