[CentOS] Confusion about scheduling tasks with crontab

Hi,

I have to setup a scheduled task on a server, and I just read through 
some crontab docs. Now I'm confused. It's not so much the syntax of the 
cron job to define (I got that), it's more... how do I get to define it? 
Use a text editor (vi or the likes) to edit /etc/crontab directly? Or 
create some empty file in /etc/cron.daily or /etc/cron.hourly or the 
likes and then edit it using crontab -e ?

Anyway, here's what I'd like to do.

I have a script:

/root/scripts/backup.sh

I want to run that script every day at 07:00 in the morning. Once. Now 
how would I go about that? The thing is: I'd like to know an orthodox 
way to go about this.

You can be laconic in your answers, I'll retrive the details in the docs.

Cheers,

Niki