I sent in 2 update letters, 2 LOR - one from my new manager ( i have been working with him for 6 months) and another oen from my fiance who happens to be a Booth alum. Apart from this, I visited the school in March after I was put on the waitlist and then attended two other local events. I wrote about these events, fit to school, professional and personal achievements etc, in the update letters. Hope this helps. Congrats to all the R3 and WL admits. Hope to see you in Chi-town soon.
Good luck to everyone else.