I keep the system very simple:

1 Have a clear reason to open, and some suit quality to support it.

2 Don’t open at the 1 level with a singleton - partner invariably responds in that and you have nowhere to go but too high! With a singleton its the 2 (or 3) level or nothing.

3 Make sure partner knows they should only bid a new suit at the 2 level with 5 cards (so you dont tumble into a difficult 4-2 fit).

It can be as simple as that! Although, there are some subtle nuances to consider for completeness: The Passed Partner ought to pass with a minimal responding hand, should be more cautious to jump-raise or level-of-fit raise, and may bid 1NT on more than 9 points (eg  with 4 clubs and 10-11 points). Openers rebid should promise 14+ (even a suit preference) - Pass with less and with more than 14 remember responder’s 1NT could be over 9, so try to give an opportunity to reveal extra (such as raising your suit preference). Finally, Opener may also open 2NT and 2C bids a bit lighter than normal, so responder doesnt cautiously pass opposite a good 19 point opener. 

It is worth remembering safe 3rd and 4th seat openings are a partnership agreement to be discussed rather than unilateral action! And suit only makes a difference whether or not you have a clear reason to open - 1C would not be premptive whereas 1S could be.