Very good, Martin0. Thanks!
I would just add this:
6. It is a Team game. If you lose your teammate loses too. So, if you do not have enough time to play a game (which can be long), just do not start it. If you have a bad Internet connection, just do not start a game until you fix it.
7. If your teammate draws an arrow, it is not an order. You should think yourself if his suggestion is good or not. Do not make an "auto-move" just because you see an arrow!
If you have ever tried teams you should know that the variant is very different than FFA. Here are some tips on the teams variant. Note that I am also still learning this variant, so my opinion on some things might change over time.
1. Communicate with your partner!
Since you are in a team it is really important to play as a team. You can draw arrows by right-clicking and dragging. Clear arrows by left-clicking. Using chat and arrows for communication with your partner will greatly improve your teams overall play.
2. Play actively!
It is really important to play actively with your pieces. Not only will this make it easier to create tactics with your partner, but you will also be able to help your partner if he is attacked.
3. Always look for tactics!
This is a very tactical variant and you constantly want to create tactics with your partner and avoid tactics from your opponents. Look for forcing moves, which are checks, captures and threats. Be very careful of checks. If you get double checked by 2 queens, then you are quite likely to get mated soon if you are not mated already. Also note that I really mean to always look for tactics. This includes the first moves made in the game (you can blunder on move 1!).
4. Develop your queens early!
This might sound a bit controversial. Haven't you been taught not to develop your queen early in classical chess? Well there are a lot of squares on the 4 player chess board and the queens tend to find squares where they can stand safely and aggressively at the same time. There are also usually no easy way for your opponents to harass the queens to get ahead in development and they constantly need to watch out for tactics (especially double checks by both queens tend to be deadly). There might be other good approaches where you don't develop your queens early, but you do not want to end up playing a middlegame with an inactive queen.
As a side note it is certainly possible to move your queen too many times in the opening when you do end up behind in development because you were just trying to checkmate early. When it is good/bad to move your queen several times in the opening is a very complicated topic that I will not cover here, but I hope you put your queen on a better square if you move it several times.
5. Don't be afraid to trade!
It is important not to misinterpret this advice. You should not be afraid of trading pieces when both teams loses the same amount of material. However, being on the receiving end of a trade where you have to recapture can often be quite risky since it might be possible for the one initiating the trades partner to create a tactic against you when you want to recapture on your next move. So make sure your move is tactically safe before offering a trade.
Finally I want to mention that this is a very tactical variant and new players will have a hard time to survive the first 10 moves against experienced players. Don't be ashamed of falling for early checkmates, everyone does that at the start. Also for those wondering how you can blunder on move 1, see this topic:
https://www.chess.com/clubs/forum/view/share-your-quickest-checkmate-or-your-favourite-one