guitars

If your strings are 10 years old, it's going to need a hell of a cleaning.

I generally like the music nomad kits, they are a bit pricey for what they are, but they are convenient if not anything else. You will want the Frine Fret polishing kit, because those frets just have to be nasty. You'll also want to grab their cleaning spray, which is a good all-rounder. If you have the budget they also have this cleaning spade that's good for getting under the strings and the fretboard when you still have strings on, like it's good for maintenance cleans while it's strung, but it's not necessary either. Just nice to have.

Start with the fretboard and move down. Clean the frets, and oil it (theres youtube videos for everything).

If you don't want to spend the money, at a minimum get a bottle of cleaner and a bottle of a fretboard cleaner if it's rosewood - if it's maple just use the general cleaner sparingly. You can use autosol and a rag to clean the frets on the cheap, but tape your fretboard up before you do (that's why those music nomad fret guards are worth their weight in gold).

Otherwise it's just common sense. Use a good microfiber cloth if you don't want micro scratches (like the ones that come with reading glasses).