That's why you have the indexing strategy, it takes all that out of it. Replicating the top 10 companies from Vanguard will remove your diversification and will cost you in brokerage unless you are dealing with large enough numbers where the brokerage costs less than the ongoing management fee.
If you want to invest in individual stocks there is a lot to learn, finance, accounting, economics, the actual business and what it does, the markets it operates in, competitors and alternatives, any developments or risks impacting on it's revenue streams.
One up on wallstreet and Intelligent Investor are two books I would recommend you start reading if you wish to learn. Also a basic level of finance, accounting and economics will help a lot.