I did much the same thing as you are describing last summer and fall. My portfolio is still primarily BRK.B, but I added the stocks of a few companies that are highly profitable and, I believe, predictable. My second largest position after BRK.B is now GOOGL. I like GOOGL's motto, 'Do no evil.' I started buying GOOGL in May at $112.89 and averaged down to $83.65 in November. I have a full position now in GOOGL, but if the stock price drops below my lowest purchase price, I'll probably buy more. Today's price of $89 looks like a reasonable entry point to me. For other stock ideas you might look at the Motley Fool Berkshire Hathaway discussion board's 'group portfolio,' which consists of 25 recommendations from members from August 8. The criteria for the picks were high predictability and high probable return over the next 10 years.

discussion.fool.com - Group portfolio update