If you're used to the US and the TSA "security theatre" involved, you should find this to be an understatement. No TSA goon checking your ID and boarding pass (what for?), generally no need to take shoes etc. off, and you may find the security folks actually smile at you and say hello. For domestic flights, it's usually a very easy and pleasant experience, with minimal lines - an altogether different experience from the US.

If you're on a domestic flight out of/in to an international terminal, the boarding pass usually has a big letter 'D' on it. I've only ever done it a couple of times and can't remember whether they asked for ID, though they may do. With that possible exception (and as thadocta says, solve it by not taking a domestic flight from/to an international terminal), I've never, ever been asked for ID when flying domestically.