I've read many of the posts here already. Once I've troubleshot to the point where I need to open the ceiling, are there steps to take when cutting the hole and then sealing it back up to make it look good? I'm not much of a DIYer, but homeownership seems to be changing all that. Thanks in advance.

My answer is based on the assumption that your ceiling is drywall. Lets start with a fairly small inspection hole. Locate the studs with a stud finder. Mark the studs and cut a hole with a drywall hole saw the width of the stud bay. Don't worry about trying to keep the old piece of drywall, its junk and must be pitched. If you locate your leak and fix it then you can add some furring along the lower edge of the drywall inside your hole, this is where you will screw your new drywall patch. Let us know what you find and maybe we can help with repairing the leak.