"Liquid Vanish" used to be the best thing ever, no streaks, no smears. Made from natural ingredients - until Reckitt Benckiser took over and messed around with the contents. Now it's crap.
Washing up liquid has salt in it to thicken it, and alkalis to counter grease. Both can leave smears after drying. (Don't use it on your car either, the salt and alkalis can damage the paintwork!).
Newspaper used to be OK till 'high speed inks' were invented. That's the ink that blackens your hands when your reading the paper. These inks are greasy, and tend to smear onto the glass. 'Newsprint' is the paper that newspapers are printed on, and is very good in itself.
Vinegar's good - it's acidic, and it cuts through any grease.
But B&Q sell 'Squeegee Off' concentrate, an American product that's somewhat pricey, but is still economical, as you only need the teensiest amount in water. Combined with a microfibre cloth it's totally brilliant. Dry with kitchen roll as it's got no additives, unlike paper tissues and loo roll which tend to have talc in them. Cloths that have been rinsed with fabric softener will leave a smeary film.
I have a total of 17 windows in my house - so I've learned by experience! ;-)