If your dog is maybe a little anxious/aggressive when meeting new dogs here’s a couple quick tips.
1) Don’t make a big deal over the introduction. Many times when people introduce dogs it’s walking head to head to another dog. This is confrontational and should be avoided if your dog is uncomfortable. Try walking up along side of another dog not directly towards them.
2) Don’t allow your dog to pull you over to meet another dog. It’s a good idea to teach dogs to sit when meeting. Once they are calm release them from the sit position so they can make formal introductions.
3) If you have access to doggy daycare use them. Doggy daycare when properly monitored are great for dogs to build social skills.