PLEASE HELP, Moving to new domain

I have been building a site on another domain, and now the client wants to move domain name. I plan on using the same exact db and just going through and changing all the links (ugh)

I downloaded everything and uploaded it to the new domain, but when i login it wont let me

So when i go to newsite.com/wp-admin it redirects me to oldsite.com/wp-admin

What do i need to edit to prevent this?