question about dev site
 

How do i properly set up a main site and a dev site? Should they be using the same database? How do i be logged into both at the same time?

Here's my current set up
domain.com
sql: domainmain
cookie prefix: dom

dev.domain.com
sq: domaindev
cookie prefix: ddev

What should i set the cookie domain and folder to in the setting of both sites? or should i start over using the same sql server?

anyone have any other tips?

I run dev version of my site. The way I did it was my host essentially copy/pasted all the files, folders and database for my forum to the dev site. You can save the cookies into the the same folder as long as you have different prefixes. Be careful to immediately change the config.php file for the dev site and change the cookie prefix before accessing anything on the dev site, otherwise you will run into weird cookie problems. This happened to me and I was accessing both sites at random off and on, plus couldn't log into the AdminCP. So just take care of that first and you should be good to go with the settings you posted.

just for clarification - I should use the same database, using the same cookie domain and same cookie folder, but setting the prefix in the config file to something diff than the other?

Different database, different prefix. You can use the same cookie domain if you want or not. I use the same one without any problems. Since the prefixes are different there won't be any mixups.