Well, always put the kick stand down first and lean the bike onto the stand before dismounting. That's MSF 101 basics. Also, hold the front brake with your right hand to stabilize the bike.
Beyond this, you just stay facing straight ahead, put your left foot on the ground and swing your right leg over as you turn your body, perhaps carrying your leg a little higher than normal to clear the bags. I don't find it takes any special gymnastics, but depending on your height, stature, and flexibility, it might be more of a problem for some.
When you start putting tail bags on or piling up the rack with gear, then it gets to be a serious issue. At this point, I may resort to dismounting hurdler style, hopping away from the bike on my left leg while withdrawing my right leg directly over the seat. Tends to scuffs the seat though.
- Mark