App rate is pretty quick too. I think it'd be a bit short for a tutorial. Here are the details:
iOS:
Just call RateApp(int iOSAppID , string AppName , string message)
This will create an iOS dialogue box with 3 options: Rate, Remind Later, and Don't Ask Again. iOS maintains a flag for these options so if the user says "Don't Ask Again" or "Rate" then future calls to RateApp will be ignored. No need to save data on this. The iOSAppID is listed in the iOS developer portal (iTunes Connect).
Android:
You'll need to make your own UI if you want. We do something similar to the iOS rate ask UI, but stylize it to our game. With Android you'll need to save the user response to the UI in a data file if you don't want to bother them again when the press "rate" or "don't ask again". When they select "rate" simply call OpenBrowser() with the following URL:
Google Play:
"market:/"+chr(47)+"details?id=com.naplandgames.sudokuinspace"
Amazon:
"amzn:/"+chr(47)+"apps/android?p=com.naplandgames.sudokuinspace"
Where com.naplandgame.sudokuinspace is the package name for YOUR app. I've got chr(47) in there because AppGameKit T1 has issues with // in string constants (reads it as a comment and breaks the whole thing). Using these URLs will automatically launch the play store application or the amazon appstore application on the user's device. Beware, though, if the user doesn't have that application installed then using those URLs will likely cause a crash.
Best practices:
We've found that users respond best to this when asked after a highlight of the game. What we currently do is after a user wins a level we show an interstitial ad but every 5th level win we show the rate dialogue until they rate or say don't ask again. Seems to work pretty well and gets more response than just having a static button on one of the UI screens. With Sudoku In Space on Android we are not giving the user the option to say "don't ask again" until they've seen the dialogue 5 times (which means 25 level finishes - 20 times ads and 5 times the rate ask - if they haven't already rated).
Really not much more to say on this front. Feel free to ask questions though. These instructions are around the forum, but a bit spread out.