2012 is already shaping up to be a good year for shareholders of BHP Billiton ( BHP) -- the $213 billion resource stock is up more than 13% already year-to-date, making up for much of 2011's poor performance. While this year's rally has been impressive, signs point to additional upside in shares right now. That's because BHP Billiton is currently forming an ascending triangle bottom, a bullish pattern that indicates a reversal in shares from BHP's October lows. The ascending triangle can be spotted by a horizontal resistance level to the upside (in BHP's case at $85), and uptrending support to the downside. As BHP bounces in between those two technical levels, shares are getting squeezed closer and closer to a breakout above that $85 level. When that breakout happens, buying BHP becomes a high-probability trade. Adding some assurance to this setup is the fact that momentum, as measured by 14-day RSI, has remained in an uptrend since August's swing lows. When the breakout happens, I'd recommend a protective stop at the 200-day moving average. BHP Billiton, one of the top-yielding metals and mining stocks, is one of Renaissance Technologies' top holdings.