I think it would be hard for someone to tell you what is "not necessary" since we have no idea of what you do/use your laptop for.
You could start by turning off services that are not needed by you. You can see a list of enabled services by running this CLI as root:
chkconfig --list|grep on
and turn them off with the CLI:
chkconfig servicename off
You will probably want to check out System > Preferences > Startup Applications also.
That should give you a place to start. Hope this helps,