I keep the system very simple:
1 Have a clear reason to open, and some suit quality to support it. (The closest approximation would be an Overcall - but made before opener has bid!)
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 don't 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). Opener's rebid should promise 14+ (even a suit preference bid) - Pass with less and with more than 14 remember responder’s 1NT may be 7-11, so try to give the 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 actions, and they still retain the accuracy of your bidding system. The Suit will only make a difference to whether or not you have a clear reason to open - eg. 1C would not be premptive whereas 1S or 2D could be.