SPY has resistance at the red and blue line. Watch these resistance lines to determine the shape of the triangle that SPY is trading inside. If SPY breaks above both the blue and the red lines, then go long.
Once SPY breaks outside this triangle, the price movement should be fast, so be ready in either direction!
However, some other people think SPY wants to close the gap around 204 (top brown line), which would require using the blue triangle to get up that high.
My plan is to go short if price breaks below the Green line, and to go long if the price rises above the blue line. For now, I am staying neutral.