I always try to do the first play through without prior knowledge, except perhaps who I can and cannot romance with my character. This actually had me puzzled first run because I had the option of flirting with everyone with my elf girl, even those I knew were going nowhere, like Vivienne, Cassandra and Dorian. Didn't take the first two but did flirt with Dorian because I was interested to see what happened. However, I found certain things annoying.
Firstly, how the war table missions involving my clan could actually result in their death. How come some war table missions end up in pretty much the same way regardless of who you choose but with others it is really important? I don't mind the fact that making the wrong choice has bad results but I just wanted a bit of consistency so I was aware of it. So where I got negative results, I checked to see where I went wrong, so I didn't make the same mistake next time round. I exiled the Grey Wardens first time so didn't get their war table missions but that was another really complicated set of choices to get the optimum result.
I also found annoying the fact that one single decision right at the beginning set Lelianna up for being a ruthless killer. I role played that my character wouldn't interfere because she was new to the organisation and unfamiliar with human ways, so she watched to see what happened. As she grew in confidence and embraced her role of leader, she was quicker to intervene if she didn't approve of some action. So I was really shocked when I ordered Lelianna not to kill someone and she went ahead and did it regardless. This meant I really didn't want her to become Divine. I made sure I voted for Cassandra and got her but I gather that had more to do with other decisions I had made a long the way rather than just my preference.
Oh and those wretched halla statuettes. Didn't realise that there wouldn't be enough to do the doors in the royal apartments if you had already used them elsewhere and didn't get them all because of the timer and having a sense of urgency; plus never even thought to look in the kitchen rafters, let alone was able to get up there. So I did reload back to the beginning of Wicked Hearts and do it all again on my first run because I felt that should have been clearer.
I also checked up to see what dialogue option I had to take to keep Dorian with me the next run with him as my romance because I had been too emotionally wrecked by Solas to want to experience another heartbreak.
So to get my canon play through I really had to meta game, which is odd because I've never really had to do that in the other two games, although after visiting the forums and discovering characters could be "hardened", I did make sure I took that dialogue option when I wanted to see what difference it made to them.