How can i make a script/service/application start-up on system boot on a debian 7 based server? (xpost /r/linuxquestions)

I've tried adding something like this to my /etc/crontab file:

@reboot root screen -dm su steve -c "/path/to/bla -c /path/to/bla.cfg" 

but it isn't running at all :(

I'm also finding it hard to find any info on how to do this another way.. any ideas?