What did you have in mind? Setting up a track day can be a logistical nightmare. An easy way to go about it would be to identify an organization that you'd like to run with and contact them about an all MINI run group. Though I haven't even seen much success with that, as you will get drivers of different skill levels. I went to one MINI specific school and even there he has a hard time getting enough MINIs to make the day worthwhile for his business. He has to let in other cars.
O.K., so you pick a group, pick a date and put it out there. I've been to a couple of track days where we had close to 20 MINIs.
Or, you keep your eyes opened for a dealership sponsered track day and attend that.