In my life, I've been on over 150 flts (I've yet to turn 23 so it's not as small a number as it might sound). Even if I don't keep records, I guess I've used about 12-15 different types of plane....from Shorts and small Fokkers to the 747.
I've used aircraft steps, platform stairs and jetways. But I can never recall boarding from the right-hand side of the plane. Nor have I ever seen a picture/film of somebody getting on/off the plane from the right hand side. I've disembarked from the middle of a plane once, flying MXP-FCO on AZ with a MD80 Super.
Is there a reason for this practice?