A good resource is:
http://www.crypt.gen.nz/selinux/faq.html
There, the most important thing is this.
It is important that server daemons are started within the correct context, if they are not then they will probably not run properly.
For Fedora and RedHat Enterprise Linux, use the normal command,
service (name) start/stop
For Debian and Gentoo, use the run_init command to run scripts in /etc/init.d within the correct context, for example sshd:
run_init /etc/init.d/sshd start
which starts up the sshd daemon. Note that run_init will prompt the user for their password before performing the function: this is to prevent unauthorised acces to the functionality such as being executed by a trojan program.
To know if selinux is installed
rpm -qa | grep selinux
To know if it is enabled
/usr/sbin/getenforce
