My first shadowing experience I actually got through my school...but then after that I was on my own.
I drove around town and asked if they were looking for an interns and gave them a resume. One place said they had no room for an intern so then I asked if I could simply just shadow, unfort. they never called me back. But it was okay because the next place I went to interviewed me on the spot and gave me a job!! 🙂
good luck! So yeah, just go in to an office and ask, or even call. =) Tell them you are pre-opt and just wanted some experience shadowing/observing the OD.