In principle you can actually walk between the two terminals at Changi, though there is also a fast automatic train type thing which take you a few hundred yards.
It is an extremely easy airport to navigate around - everything is signed in English and everyone who works there speaks English.
There is, of course, a website with full details:
http://www.changi.airport.com.sg/
There are plenty of places to sit, places to shop, a internet-browsing lounge (presumably censored to the usual Singaporean government standards) and also, if you want, there is an airside transit hotel which I imagine can be rented by the hour.
Hope that helps