Clan Battle in general
This new game mode is completely different from the regular game mode and you have to adapt to it.
Every one of you will play his own deck and have his own Elixir Bar, so you’re not playing with a “shared” Elixir Bar. The Elixir production, however, is only 70% of the regular production (and 85% in double Elixir mode) to prevent just a chaotic spamming of troops.
I think you see that working together is the key as you just won’t have the Elixir on your own to make strong pushes while defending at the same time.
Communication in Clan Battles
You will always see when your friend is about to drop a troop off, that’s already a valuable information – you see that when a card icon is appearing on the map:
Now you can also see what cards your partner is able to play by clicking on his name right on top of your bar: