Patching Redhat v6.4; v6.8; v7.1 and CentOS v6.5

These systems have never been patched. What is the best way to go about patching these systems to ensure nothing breaks along the way. We are not currently using Satellite. This is a small Linux environment.
1) How to determine the latest patch set for Redhat v6.4; v6.8; v7.1 and CentOS v6.5?
2) How to determine dependencies?
3) Do the servers need to be registered with Redhat in order to download the patch set?
4) How to download the patch set?
5) Is there a standardize procedure for downloading and installing patch sets? If so where can I find it?