There needs to be a concerted effort made to make people feel welcome. A guest to your church does not need to feel as though they have to break through invisible walls to get inside the social structure of your church. My wife and I once visited a church in our local community in the same denomination in which I grew up. We were different than most visitors in that we went early for Sunday School. Our goal was to make friends and really begin to "connect" to our town, so Sunday School seemed liked the place to start.
We got to this church early and went inside the building along with two-dozen or so others. We got a rudimentary "hello", and nothing more. At all. We took a seat in the back and proceeded to watch as a little group gathered to our left and began to carry on a conversation. We observed people at the front of the room talking with each other, and to those who came and went through a nearby door. Everyone there seemed to know each other well, and seemed quite content to let us sit there alone. I believe they seriously expected us to make the first move.
That is not the way it should be done. But, eventually, we did make the first move -- to our car. before service ever started we left.
So, what should be the modus operandi? Well, try this instead. Have greeters in the parking lot. As people drive onto the property, greet them with a wave. Point to open spaces if needed. Be sure they have umbrellas available when it rains. Then, have someone to open the doors for them as they approach the building. Once inside, direct your people to a "Welcome Station" where they can be formally greeted, receive a bulletin, receive a gift (if they are a first-time guest), and get a name tag.
You have probably noticed two things at this point. The first is the use of the word guest instead of visitor. The word guest is better because it connotes an idea of friendship. A guest is someone you know, someone you value, someone you want to know better. In the above story I used the word visitor to describe my wife and I at that church. Visitor suggests someone who will not become a friend. Someone who will not be around a long time. As we weren't.
A second thing you may have noticed is that guests receive a name tag at the Welcome Station. In fact, everyone gets a name tag. That makes for much more personable communication. Church size doesn't really matter here. I know of churches with 3000 weekend attendees who do name tags. But I think it is imperative for smaller churches or church plants to do them.
Here is why. Everyone in the church should be on the "Welcome Team". Early in the service, stop what you are doing and give people 3-5 minutes to mingle and make friends. In a contemporary service this can be done midway through the "praise" portion of your praise and worship. if you have trained your regular attendees well, they can move around to people they do not know, but still be able to greet them by name. And vice versa, which is easily most important. It really will help guest to feel connected to your church from the very beginning.
I know of one plant that decided not to use name tags. The biggest problem with that is it made it more difficult for guests to get connected, and feel connected. They are a very friendly church, but even after 6 months of attending, folks I know reported that it was hard for them to feel "a part" of the church. And as a result, I believe that church did not grow as quickly as it otherwise could have.
In addition to these other ideas, use a bulletin with a "tear off sheet" for registering attendance in services. Make it a goal to get all people in attendance to sign one and turn it in during the offering. That makes it possible for you to contact first-time guests later in the week. In fact, it is a good idea to make a "thanks for being our guest today" call that very Sunday afternoon. It makes quite an impact.
Another idea that works well is to have a regular (monthly or quarterly, depending on rate of growth) meeting where recent guests can "Meet the Pastor". Recruit a team that can produce first-class eats. Have some printed information about the church available. Possibly produce a video or PowerPoint presentation introducing your church to your guests. Use this time to not only connect with them, and them with you, but for each of them to connect with each other.