I think we should keep this thread rather broad, so please dont ask questions about your super special builds. I guess focussing on Arena would be a good idea, but dont hold back your super interesting spot just because it isnt Arena
If your question is from Constructed, please add as much information as you can. What deck is he playing, what cards did you use before, maybe you met him before, what did he play then etc. This wont be as important in Arena, because Arena is most of the time just about board control.
Lets start with this, Arena game with an interesting starting hand. Whats your line there for the first three or four turns?