E is really tricky, but try to use your index finger for the G string, your middle finger for the A string, and your pinky finger for the C string. For B (and Bb) use your index finger for both the A and E strings, your middle finger for the C string, and your ring finger for the G string. For Bm, use your index finger for the A, E, and C strings, and use your middle finger for the G string. These positions work for me, even though I have trouble getting a clear sound from the A string for the B chords. If this happens to you, don't worry! Chances are you won't even be able to notice if you're strumming. If you're still having trouble, try to transpose the song up or down accordingly so the chords are easier.