Mr Light wrote:
I finished the Earth-Mars-Citadel opening and can free explore now. I recall reading somewhere that the new planet scanning thing can prevent mini-missions from being played, how does that work? I do the scan pulse, it shows me which planet has something, I scan it, I pick something up. Where does this lead into mini-missions?
you might be referring to journal entries that ask you to retrieve various items from scanned planets, then return those items to people on the Citadel. You can receive those missions from ambient dialogue while on the Citadel, or after finding a given item by scanning its planet before you've even heard that someone needs it. These items will assist in War Assets for various reasons (some are simply for morale; some will inspire people to their better natures; some will be useful for the big "win the war" project; and so on).
The thing to remember is that doing priority missions can cut you off from certain side quests.