*some vague spoilers below*
It's very hard to ruin the chances of romancing a character, the game will make that easy at the end of Act 3, when you're in the Hall of Echoes on Lady Vengeance. However, it can be rather easy to miss out on some cool moments and developements. This happens because alot of these interactions are timed (beats me why Larian built them this way), so you can miss the chance of having certain interactions if you don't do it within a certain time frame (some, like Sebille's song quest, expire REALLY fast). Also, some conversations will only trigger once, if you don't take them you might loose the chance for good.
At the end of Act 3 you'll be able to initiate a romance with any character that has high enough attitude towards you (min 50, I think), and enjoy the biggest romantic scene in the game.
Also, keep in mind that in DOS2 you don't get many romantic convo options after you get intimate with a character. These are few and far between. It's not like soemthing like DAI, where after you initiate a romance you can always choose to flirt or get hot and heavy till the endgame.
I could make an entire post about how the romance and the endgame world state in DOS2 is lackluster, but who wants to hear that... With all it's flaws, it's still one of the best games I have ever played.
I only saw the date on this thread after posting. I hope this helps other people with the same question though.
Last edited by Spellsave; 04/12/18 07:36 PM.
Personally I stayed away from any "romantic" exchanges. Call me old-fashioned or whatever, but I really prefer the more subtle, elegant, and gradual romances in games like Baldur's Gate or KOTOR or Dragon Age. Romance in DOS2 is... ehhhhh.. not for me, I guess. Or maybe I'm just old.