While some fall in love, others are into flings. Some of the NPCs are quicker to “join you in their tent” than others. Most of them were good friends with those who weren’t romantically involved. They’ve romanced Alistair, Zevran, Morrigan, and Leliana. In the course of playing Dragon Age I’ve played male and female Wardens both. I hadn’t given him his mother’s locket, yet, but I did use some of his other Gifts to get him to the point. I had to get a little farther in the game before he was ready to spend the night with my Warden than I usually do, but it wasn’t too far from this. The unique gifts (his mother’s locket and Duncan’s shield) seemed to boost approval much more on the console than they do on the PC. This is for the PC version, but it should get you close on console, as well. The approval rates vary slightly from the PC. Note: I had an opportunity to play on the PS3 recently. Obviously this entire post is spoilers, so don’t read it if you don’t want to know specifics about Alistair.
There are posts for other characters as well.