Beside all the technical stuff ( which is of course necessary, but you must find out what’s the best for you) checking out the market sentiment before the opening is very profitable. With some experience this offers you the possibility to make within seconds after some mouse clicks the pips for the whole day.
15 minute charts are great although you’re going to have to move to larger charts to understand the overall picture. Trading session opens where the quality is at its highest is probably best. Do you want to identify what is going on during the opens and then ride on those trends.