i've played eb for a couple of years, and this is just stuff i try to think about while playing:
-really tighten your embouchure, it's a smaller mouthpeice so you'll have to anyway, but you'll have more control if your embouchure is really firm.
-blow! don't be afraid to put air through your horn (even on high notes); as time goes on you'll get more control over your volume and will be able to back down a bit...but nothing sounds worse than a half choked squeaked out high note (i should know, lol); plus more air will make everthing you play sound better
-tuning has, and unfortunately will always be, a problem. putting air through your horn will help, but for the most part you just have to find out your tendencies. i played every note on my horn in front of a tuner to figure out how i normally was, and how my mouth felt when i was in tune. then in concert band, i just had to listen and try to compensate (which is really hard)
-as for high notes, the main thing for me was to blow, tounge lightly, have a tight embouchure, and have my fingers directly over the holes
another random tip: i do chromatics and scales every time switch from Bb to Eb, so i get used to the smaller size of the horn and spacing of the holes.
I hope this helps! good luck!