First off, God bless you for your willingness to pursue the calling he has for you in life. Know that you are in my prayers.
The initial meeting, at least in my experience, was just for becoming acquainted. I told my Vocation Director a bit about myself, my background, my prayer life, etc. I asked him questions about the timeline, so to speak, of seminary formation and other things I wasn’t clear on. Ask whatever you like, and don’t expect that this will be anything too intense–it will likely be mostly informal. Dress nicely (I’d say minimum of slacks and a polo, perhaps a shirt and tie if you’re so inclined), be on time and polite, and relax.
Hope it goes well, and feel free to PM me with any questions.