I'm not one of those who holds with @Retreater's despair over SCs. They work WELL, and between the DMG, DMG2, and RC the sum total of the updated advice is not bad.

Basically you have, as of RC, your success threshold, which skills are considered primary, and then how many free advantages and how many difficult checks the DM is allowed to require, plus the list of secondary skills. It is up to the DM and the players to work these things into the narrative.

You need a dynamic narrative, with genuine conflict which engages with the PCs goals and plans. That can be fairly simple and basic for a Complexity 1 SC, but generally it will mean some real plot engagement for most SCs. Frankly I would take the idea that you are authoring the SC in detail up front with a grain of salt. I would prefer to think in terms of Story Now style 'scene framing' type play, where the players choose the general direction and approach, and the GM brings the conflict into a scene somehow, which in this case results in an SC.

TBH I don't have a radically different approach with combat encounters. Help something unfold that moves the PCs forward on their journey in SOME direction. If the players decide to put up big stakes, then make the potential rewards equate to the risks! This goes a bit beyond what the RC rules actually talk about, but I think the idea of advantages and difficult checks can be made to play into that dynamic quite well.