Having been to several, I can offer some advice.
1. Bring some snacks that you can carry with you and some bottled water. The food at conventions tends to be expensive.
2. If you're getting a photo op with Dean and want a special pose, be ready to tell him immediately. Photo ops tend to move quickly, and you won't have time to think of something on the spot.
3. If you want more time with him, consider buying an autographed photo. Those tend to be just a bit slower paced.
4. If there's anything special you want to say to him, think about it before you get there so that you don't let the opportunity pass you by.
5. If you want to actually make physical contact with him, don't be afraid to ask if it would be okay to get a handshake or maybe even a hug. Just remember to respect personal boundaries, and don't place your hands anywhere disrespectful.
That's all I can think of for now. If you have any specific questions, feel free to ask.
