Hello desp13. I feel for your situation. You mention sometimes using the excuse of asking about your daughter. One thing that I cannot impress upon you enough is that it is now all about your daughter. I know you want to be back with your X, I know I definitely wish I was back with mine, but the more important thing to me is that my son is doing well. Don't use her as an excuse - use her as a connection. Bond with your x based on the love that I'm sure you both share for your daughter.
As for mistakes to avoid - I would say play it cool. Don't let your emotions get the best of you. I genuinely think I would be back together with my X if I hadn't been so angry towards her during this time. Stay calm when you see her. Appear happy. It hurts to fake but trust me, you're better off.
Best of luck.
Me 23, Her 21 1S 2 M <1yr, T 7 WAW: She moved out 11/15/2014 She started D process 1/29/15