The ultimate shortcut when you cannot figure out how to get your glass streak free is to get a professional to do it. Okay, fine... That's a dirty answer. We know you need to know how to do it between service intervals.

So here it is:
Buy a decent automotive glass cleaner. I recommend CarPro Clarify which is available at Detail Depot. This is because household glass cleaners usually have ammonia in them. Ammonia melts plastic. Window tints are made of plastic, so this is really only a concern on the interior of your vehicle. Don't worry if you used the wrong product a couple of times. You'll only cause damage with long term use and window tints are replaceable.

On a fine, low humidity day use two clean, lint free towels. One for the product, and one for drying. Spray once on the first towel before wiping onto the glass. Avoid spraying onto the window directly as it will flash off too quickly. Especially in warmer weather. Make sure the window you are working on is completely dry before wiping again with the second cloth. If you get it wet you will need a third...
Sometimes you will have to repeat this more than once. Most likely on the inside of your windscreen(that's always the worst window, unless you have kids or dogs).
The key here is not to use too much glass cleaner. Without the ammonia it is a wee bit more difficult to keep streak free. An overly humid or wet day will also affect the result, as will direct sunlight. If you have a nice dry and well lit garage, do it there. It will make your task easier.
Avoid oil based(silicone, think Armour-All) treatments for your dash. The oil evaporates and hazes up your windscreen when the sun is out. You should also consider this when picking an air freshener. Pick up one that is made of card-stock instead.  You can put your favourite perfume or cologne on it when it fades too. Recycle!

Sound too difficult? When you book me I will give you a live demonstration.

What about water spots? This can be really subjective. If they are new water spots, they come off easy. If they have been there for years it'll take a lot more time and require machine polishing, only to come back if you as the owner do not keep up with maintenance. Ask me how to keep them away when you call.