So Just Briefly for anyone trying to Romance Sear (IMO the only person worth romancing) , its a little tricky because Id played the game till about 50hrs and after I did the temple of mythal the romance availability gets locked out. What this means is that no romances can be entered into at all. Its very frustrating the best advice I can give is before any crucial decision ie: Any scenario that has you traveling to a new location after spending power,save your game. Ever opportunity to gain approval take it BUT NOTE that small drops eg: when you talk to sera and you say "But your an elf" and it goes into a bit of dialogue about her distain for elves she will show a slight dissaproval . This is nessecary becuase as others have commented all avenues of conversation have to be removed before the special loveheart function triggers the cut scene. This is the path I chose and I started my romance with Sera at 20hrs then I loaded a game that I thought was bugged and started it at 45hrs.
Be self effacing, Choose the littel people ove the bigger picture, Make quick decisive decisions about executions. And exhaust dialogue with her even the parts about her pranks being really nessecary and being an elf, these are trigger points.
As far as I know the romance can be started as early as just after opening skyhold. And the results are definately worth the effort