Human beings like to talk. We talk about everything which even remotely interests us: the weather, politics, cars, sports, fishing, movies, make-up, hair styles, clothes, food, you name it. (We even talk about things we shouldn't be interested in, and that's called gossip, and gossip is a sin.) The more we like something, the more we talk about it. Consider: when was the last time you saw a favorite film and never spoke of it? Have you ever thoroughly enjoyed a book or album or concert and never mentioned it again? Of course not. We tell other people about them. It's simply part of who we are as social creatures.
We should treat church the same way.
It's a proven statistic that the average person who doesn't attend church will go if and only if someone invites them. Part of that is being polite, I'm sure, but it's also the fact that enthusiasm is contagious. Inviting someone face-to-face shows them you love your church, you're excited about it, and you want this person to share in that joyful, holy experience. It also shows you care about them enough to be concerned about the state of their immortal soul. Love goes a long way, folks.
Odds are that God's not calling you to stand outside Kroger and hand out tracts (but if He is, you'd better do it). Still, we all have the duty of evangelism, to share the good news of Jesus Christ with those who don't yet believe. One dimension of that is simply inviting people to church. Even if you're not comfortable directly sharing the gospel, you can ask someone to go with you to hear a preacher do it.
So if you want to show love to your neighbors and help grow your church, tell your friends about it. Invite them to worship. Let them know Christ died for them -- and that's good news!