Don't be afraid to let others watch the baby
My daughter was a mere three weeks old the first time we left her with my parents-in-law for an evening. As we pulled out of the driveway, I couldn't stop the tears from flowing, but we ended up having a great time at a holiday party, and the baby was perfect. It's important to get out as adults every once in a while, and we've found there are people lining up at the door to take our kid off our hands for a few hours.
Make friends with other young families
Since the baby came along, it can be somewhat difficult to maintain friendships with single people or couples without kids. We're not as flexible when it comes to timing or location of plans, and the baby can be a bit of a distraction when trying to talk. Making friends with other young families makes socialization easier. Even if we don't get in a lot of quality conversation due to distractions, at least we understand the chaos, and when the kids are older, they'll be able to run off together and play while we have some adult conversation.