Try to hook up with an owner that is experienced in dog park behavior and ask questions. Remember though to always get a second opinion! The tough part is to stick close to your dog and protect him if he needs it. Dog play can sound loud, get physical, and involve chasing so it takes time to know your own dog's behavior and learn what is appropriate for all parties involved. It sounds like he is a puppy so beware.....wonderful dogs can feel compelled to "dominate" puppies so if you see him on his back more than not it is time to separate the dogs and move on. Don't hesitate to shoo the other dogs away, remember you are the "alpha" and your dog is looking to you as a parent to keep him safe. Keep walking also, most problems occur while people are congregating in a clump and dogs can get protective. Allow your dog to "pick" his own friends and just like you don't like everyone you meet, your dog won't get along with all other dogs. Some days I take my dogs and they just don't "click" with the dogs there that day so I don't force it, leave, and come back another day. The dog park is for them not us so first and foremost ensure they are happy, safe, and well behaved. Good luck!