My advice to you, DO NOT get anything darker than 20% on the front windows. You want to be able to see out at night.
5% is very difficult to see out at night when there is no light around, or even in lit parking lots you may not be able to see pedestrians behind you or other obstructions. Plus, during twilight hours where the sun is rising or going down, people that have their head lights off are INVISIBLE. You will get into an accident, ESPECIALLY motor cycle you will not be able to see them. Even with lights on some times, the blinding light/glare during these hours with a DARK DARK tint makes it impossible to see out. Use your head. Same goes in severe down pours or bad visibility conditions. Again, you want that balance.
If you tint the back window, do NOT go darker than 20%. You want to make sure you can see out, and if you have a COP behind you, you want to make sure he can see in within reason so you don't get stopped for a tint violation.
The rear side windows, I like to use a 5% personally, it gives privacy to the passengers in the back and just looks pretty cool.
Putting 5% all around the car, bad idea. For safety and for the risk of getting stopped.
PERSONALLY, the best balance all around is 25%. It's dark enough to offer some privacy and block the heat out and you can still see out fairly good at night.
When it comes to cleaning tint, MOST tints you can NOT use ammonia based cleaners, it will ruin the tint. How ever, VIPER tint I believe says you can. There is a glass cleaner called Invisible Glass which can be found at Wal Mart, it comes in an Aerosol can and claims tint safe. I've used it with no issue.
DO NOT get cheap tint either, find a reputable tint shop. Make sure they aren't using some cheap China tint. Often times they will lie. 3M, LLUMNAR, VIPER, etc. Good tint, there are others. On one car I had tinted, after a few years the tint became blurry and in places started to come loose in corners. I've not had very good luck with GILA tint either, it seems to turn purple or have a purple haze. From the outside, it looks black from the 5% I bought. From the inside, a purple haze is noticeable.