If one's entry into the church is solemnized by baptism, then how does one leave the church? If one's entry into the church is solemnized by baptism, then how does one leave the church? What are the ways that one may leave the church?


apostasy
backsliding
heresy
blasphemy


Is there a way to leave the church with a good reputation? Committing apostasy, backsliding, heresy, and blasphemy all sound like bad things. For instance, if a person does not commit blasphemy, heresy, backsliding, and apostasy, but still leaves the church out of a personal disenchantment or disinterest of the visible church, then would that still be considered "leaving the church"?
There is no biblical precedent for formal disassociation with the church, other than excommunication.  Excommunication is a church censure for some gross act for which as Paul says, one must be "handed over to Satan," with the idea that the offender will repent and (hopefully) be reinstated.  1 Corinthians 5 goes into this. One might be excommunicated for blasphemy or active, persistent heresy, but it would be rare indeed for simple backsliding to be the cause.  In Amish circles, you might be shunned for for your behavior, but that is a different matter indeed from actual excommunication. 

As a practical matter, excommunication in a body that is now a voluntary association is now thus a very rare thing.  It takes a special individual to voluntarily remain a part of a body that  has formally expelled him.  As such, while it is still "on the books" so to speak, it's rarely used.  

Furthermore, since excommunication comes from the church rather than the individual, there is still the question of how one would leave voluntarily.  Indeed, many Christians - especially those who believe in eternal security aka 'perseverance of the saints' would say that once saved, you're always saved, and as such there is no ontological means by which one could renounce their salvation.

From 1983 until 2009, the Catholic church recognized defection from the same but has since rescinded it.

To fill this "gap", some atheists have created 'unbaptism certificates' and others have devised makeshift ceremonies, but these are mostly jokes. Indeed, probably the most famous - Count Me Out an Irish group -  formally closed its doors on August 8, 2013, because they acknowledged the church has no official means of voluntary departure. Madelyn Murray O'Hair in particular liked to issue 'debaptismal certificates'.

In practice, what most people do is simply stop attending church.  There have been no laws forcing compulsory attendance in a church in the US since the Bill of Rights, and I am unaware of any Christian country that still has any such laws on the books. (Muslims, different story, but no legally enforced Christian compulsion to attend service exists). 

As far as one's reputation goes, that's strictly subjective.  Most Christians will "respect" anyone's decision to leave, but there's no way anyone would be happy about it.  If you're lucky, Michael W. Smith might write a sad song about you, but that's probably as far as it is going to go.