If you don't normally play 3s....please...do this one thing
Research. And when I say research I mean research what the current meta is. Research what are the strong picks. Research the different comps. Just research please. And if you decide to pick one of the stronger picks, please understand why they are strong and how to use them. I'm really irritated trying to make that last jump from S2 to G5 and constantly dealing with people who don't understand rotations or what to even do in 3s for that matter.
Or the most tilting thing...the ones who jump into ranked 3s while never playing a normals and then asking why we have no trinkets to lay down.
[slayer-jinx-unamused]