On a steep incline, I usually use the handbrake. The e90 have hill assist and therefore I use the handbrake rarely if ever. If incline is very steep, even the hill assist may find the car move back a little. Never balance clutch and throttle, that's a clutch killer.
If using handbrake: 1stgear/declutch/apply gas and as soon as you feel the car's rear squat, release handbrake while applying more gas. You will have tendency to release clutch fast, don't give in to that temptation or you would stall car. So clutch release same, just more gas than usual. If done properly, car would not move backwards an iota even on steepest incline.....
