Cleaning window glass on the inside

Usually several gentle applications. The tough part is the rear defroster. You almost have to work like it's silk or something fragile as you don't want to damage the traces.

Windex with finest grade steel wool you can find (example #0000). Steel wool will take off old cigarette smoke, glue residue from window stickers, and other nasty stuff. Get the window nice and wet with the cleaner and then use the steel wool. You don't need to scrub it hard, just gently move it around the window. If it's really nasty you will need to clean it again with just window cleaner and a rag. Do not use it on the rear defroster window though or you will ruin it.

There's a kitchen cleaner called Bon Ami - a very fine abrasive powder that works very well on glass. It will remove built-up grime and not scratch the glass.