Nice guide here

I was unaware that Apache comes preinstalled with OS/X

In a nutshell ∞

• All the relevant files are at /etc/apache2

• Starting, stopping, restarting the service is done with

sudo apachectl start
sudo apachectl stop
sudo apachectl restart

• The default document root is at /Library/WebServer/Documents/ but you can create a different document rule for your user by creating <username>.cnf at /etc/apache2/users/

• The following fixes a problem of connecting to MySQL from PHP:

sudo ln -s /tmp/mysql.sock /var/mysql/mysql.sock

For more details, check the above link.