1) I never ever ever ever ever bring up ex's. Neither should a female. I wrote a blog recently on my blog page about why girls should NEVER bring up an ex bf to a guy. It's not the time or place. The past is the past for a reason so keep it there. Ex's aren't in the picture for a reason, so why bring it up? Why even want to know? I am confident and comfortable enough in my own ways to not really care about what her ex did or was like. The topic is about her and you. So, if she does bring it up, say this and simply this.. "Let's talk about the good stuff in life, like us right now." Whenever I even meet a girl and she mentions she is "seeing" someone i throw out something similar like "I don't want to talk about your problems today. Let's focus on tonight and the fun stuff."
2) Eventually it is okay to throw out a compliment on her looks, but when it is well deserved. Like after you two are officially together and she puts on a stunning dress for you, or when she is wearing sexy lingerie for you. I don't ever throw out a compliment on looks unless it is EXTREMELY deserved. And that rarely comes after 5-6 hang outs. They hear it all the time, so you also have to be quite creative in what and how you say it. Say something she hasn't heard before.
3) Projection of interest should be guaged on the level you two have established. If by any means you two become official, then it becomes quite natural for you to show your feelings. Some girls are weird and are all insecure and nothing you do or say will ever be enough, but that is besides the point. Assuming she isn't like this kind of girl, the best game you have is the natural game that just comes out eventually when you have established this level of comfortness. This doesn';t mean go around professing your feelings like Shakespeare, but let the things flow, but be smart about it.
4) The only way you can find out how interested she is in you, is as the previous post states. Judge it by the ioi's, Kino, etc. You will get a vibe. My best advice for this is this... "If she clearly likes you, you will clearly know. Don't second guess yourself. You just have to believe it and know." ... I recently started seeing a girl I am extremely into. She is awesome and i like her, however, because I usually don't fall for girls, I was nervous that she wasn't into me (yes, even I get nervous). However, I just told myself, "don't be dumb, she clearly likes you. Who wouldn't?" And guess what? I was right. This is where your confidence will be challenged, so just tell yourself, I am to die for. Then your attitude will begin to believe that thought and you will become that thought.