It's been a great year for shares of Berkshire Hathaway ( BRK.B). Shares of the mammoth conglomerate have rallied more than 14% in 2013, besting the broad market by a wide margin. And now it looks like we're approaching a good buying opportunity for Warren Buffett's firm. You don't need to be an expert technical analyst to see what's going on in Berkshire's chart. In fact, Buffett himself could probably figure it out. The $250 billion stock has been trading within an uptrending price channel since November's broad market bottom. That price channel gives traders a high probability range for Berkshire's trading to remain within, a big advantage when trying to figure out what to do with this stock. The most important level to watch is trendline support; it's a level at which Berkshire has been able to consistently catch a bid. And now shares are testing that critical level once again. When you're looking to buy a stock within a trend channel, buying after a bounce off of support makes sense for two big reasons: It's the spot where shares have the furthest to move up before they hit resistance, and it's the spot where the risk is the least (because shares have the least room to move lower before you know you're wrong). Wait for the bounce in Berkshire before you decide to put your money on this trade.