two drops of washing-up liquid per bucket of warm water. A soft, clean hand-brush. Lots of clean newspaper for polishing off. Be sure all dirt and grit is gone from the glass and frame before you start polishing, unless you like scratched windows.
Can't recommend e-cloths enough for windows (the actual brand, not any old microfibre cloth) - I blanched at the £10 cost initially, but as my mum is not the type to rave about household tips willynilly, I thought I'd risk it.
You only need to dampen one cloth and then dry off with the other, so you don't need any chemicals at all. It's just as good for the outsides, too, and means you'll never have water dripping down your sleeve in the middle of winter when you can't quite reach the top of the pane. Honestly, I get all evangelical about these things - sorry!