The one thing I know is I don't know anything for CERTAIN. Stocks can and will fall farther than you think possible or seems reasonable. The best thing I've learned is patience, a stock is never getting away from you. You never know the exact bottom, buy smaller than you think is reasonable, buy more the more it falls. I've always been decent at being able to buy when stock is on sale but I've always had a tough time parting with shares and selling the spikes. It takes discipline but its worth it so I'll keep working at it.