You need to use a proper glass cleaner and newspaper is the best for glass/mirrors
I normally use Mr Muscle and some newspaper and never get any streaks
Here is a trick for you, if you wipe upwards on the outside and then across on the inside you will see any bits that you may have missed! You can do it the other way of course too
If you have washed your car in this heat its going to get like that, if not streaky then LOADS of water marks, i would suggest leaving washing until later on at night or not bothering when its this hot as your causing more work for yourself
If the windows are REALLY dirty with bugs and grime then you may need to use something a bit stronger