It is pretty easy to make an installer, if you want to make it uber pretty it requires a little more work, but for the most part its pretty easy.
Things ive learned though: make sure your uninstaller doesnt remove rgss102e.dll lol, be careful with update installers removing files you still needed(caused by typo to be fair), other small things i will point out in the tut if i make it
edit: here are the subjects i was thinking about covering, did i forget anything?
Basic(All Basic include Licence, install fonts, and Read me):
How to make an installer using the rtp(without rtp installed on users computer)
How to make an installer using the rtp(with the rtp installed on the users computer)
How to make an installer using your own custom graphics
How to make an update installer for any of the above installers
How to make your own rtp installer (amazing for making resource packs)
How to make your own installer using your own rtp
Advanced:
Making your installer pretty
Custom setup types(eg: Full, Typical, Custom)
Multi-Language support
Passworded and Encyrpted installs
Digitally Signed Installs
Silent install
create shortcut for game on quick launch bar
Making backups before replacing files