Make sure you are always checking out the Keepa graph. If you see something constantly changes from say $13, to $18, back to $12, up to $17, etc., So if the price is low, chances are it will go back up again, and if it's high, chances are it will go back down again.
Use the past trends to predict the future. If it seems very unpredictable, then maybe start very small on your order just to test the waters and ensure you do not gamble on the product.
How do I know if the buy box price will change?
How can I tell if the price of a product will increase?