I myself do not know any programming but HTML & CSS. When I need programming work done on my website I always hire someone to do the work for me.

Is their any thing that I should be worried about when giving them my server information to work on my website?

Is their a way I can back things up before tehy work on it so they won't lose all the valuable information?

Set them up their own account, or set up a temporary domain for all your development work to be done on. Once it is tested then you can migrate the code over.

I.E. yourdomaindevl.com or yourdomaintemp.com

Then set up the .htaccess file for that account to disallow any robots so that it never gets indexed.

It's a good way to develop new sites and test new code without affecting your live production site.

Yeah, Thats a good idea. What's the best way to transfer my site over to another website domain when it's ready to launch.

I usually give the original domain name and cpanel information so they can create databases and stuff

But they can delete everything if they wanted...

Have them code everything the is domain specific with a config file.

So, when they produce the code, all the information that is website specific is kept in one file. I.E. Database names, parameters, passwords, etc.

That way, when you copy things over, all you have to do is set up the new databases on your domain, and set the config file to connect to the databases you set up on your domain, rather than the ones that were on the temporary domain.

Another good way would be to use localhost database server names and, as less as possible, a remote server (like mySQL for instance). This way, once you'll transfer your content into your new domain name's location, it is highly unlikely programmers would be able to make further modifications. ;)

Use professional service.

Peace,