[SPOILERS AHEAD REGARDING COMPANION AFFECTION] - This is a copy/paste from my comment on the Astarion page because I thought it might be useful to some people here as well.
I seen a few people wondering how to gain affection of certain characters, and for those of you interested in starting a love story with... Well, anyone, I thought you might find my experience interesting:
Originally, I didn't mean to romance any character at all. Not because there is anything wrong with them in particular, but none of them really felt like a good fit for my ranger lady. Astarion is cool and all, but his preference for "evil" choices made him a "nope" for this particular character's playthrough. Gale and Wyll just felt rather ... Ehm, not really into-the-wilds enough, so I just thought I'd ignore the entire affection-run entirely and simply roleplay my ranger and just deal with whatever negative/positives that comes along the way.
So, all in all my ranger has a personality more suited for Wyll / Gale (meaning she's generally a "good" person, wanting so save innocents - but she dosn't hesitate to kill those she deem deserving of it). Most of my calls are neutral and I've had disapproves and approves coming in and out from all of my companions (I really thought I was pretty much on neutral ground at best with most of my followers). However, after defeating the goblin leaders, during the celebration in your camp - ALL 3 OF THE MALE CHARACTERS SHOWED ROMANTIC INTEREST AND WANTED TO SPEND THE NIGHT.
I have not chosen any flirty options (that I am aware of) prior to this event - I did however let Astarion suck my blood on that one occasion, and then I asked him to stop at once. That's it. I even ignored my companions for most part, pretty much only speaking to them when they had the yellow " ! " above their head. Out of curiosity I accepted Astarions suggestions to spend the night - and the other two, Wyll and Gale, immediately expressed jealousy (literally out loud, but not in a immature way) when interacting with them afterwards (I interacted with ALL available NPCs during this evening just to see if there was any hidden conversations - the reason I talked to Astarion first is cause he had a " ! " above his head).
So what do I want to say with this? Unless you're literally roleplaying a perfect-fit partner (or testing how much the affection scale matters) for a companion; just do your own characters roleplaying - you don't have to backtrack each time you see a "disapprove"-marker. It really does not appear to be very difficult to create a romantic relationship with a companion, even if your character and the companion don't see eye to eye on everything. (like I said, I've had negative and positive reactions from all of them)