We can learn quite a lot from the Church that Alma the Younger helped establish.

1) It was very friendly to new converts and very missionary focused.

A couple of verses illustrate this point:

2 And it came to pass that whosoever did not belong to the church who repented of their sins were baptized unto repentance, and were received into the church.

5 Now I would that ye should understand that the word of God was liberal unto all, that none were deprived of the privilege of assembling themselves together to hear the word of God.

6 Nevertheless the children of God were commanded that they should gather themselves together oft, and join in fasting and mighty prayer in behalf of the welfare of the souls of those who knew not God.
The members were welcoming and inviting to non-members and they regularly joined in fasting and mighty prayer for the welfare of those who did not know God. I love the description of the word of God as liberal unto all. All were invited and welcomed by all.

2) The Church employed membership standards and excluded those who broke their covenants.

The unrepentant were excommunicated. And those who refused to denounce wickedness 

3 And it also came to pass that whosoever did belong to the church that did not repent of their wickedness and humble themselves before God–I mean those who were lifted up in the pride of their hearts–the same were rejected, and their names were blotted out, that their names were not numbered among those of the righteous.

These two traits can and must go hand in hand together. The Church must be willing to welcome everyone that it can, but also enforce membership requirements and exclude those who are errant and unrepentant. These two things seems like they are in tension, but in reality both are essential components of Christ’s church.