"Because they could not hear each other, they made drums and bells.
Because they could not see each other, they made flags and pennants.
Therefore, in day battle use more flags and pennants; in night battle use more drums and bells.
Drums and bells, flags and pennants are the means by which one unifies the ears and eyes of the people.
Once the people have been tightly unified, the brave have no chance to advance alone, the cowardly have no chance to retreat alone.
This is the method of employing the many."
Organizing a team through communication is a key component of winning battles in WoWP. In the very next verse, Sun Tzu warns:
"Do not engage well-ordered pennants."
Teams that communicate well (even ones made up entirely of random players), tend to do much better overall than teams where everyone is trying to guess at the strategy or just run off on their own. The first thing to learn about communicating with your team in WoWP is understanding the various flags, pennants, drums, and bells you have at your disposal.
Here is a link to Wargaming's Guide to Battle Controls.
The most important and often used are the battle chat, chat commands and mini-map. Learn to use these HUD controls as soon as possible - first by paying attention to what your team mates are "saying", and then using them to coordinate the team yourself. The caveat here is that anyone on your team can issue commands - as you gain experience you will be able to discern between good ones and ones you should ignore or outright counter with your own commands. Use the Roger! (F5) and Negative! (F6) keys to quickly communicate your acceptance or rejection of the command. As your mastery of the game increases, you'll be able to more easily recognize good ideas from bad ones and even lead a team of 15 randos to victory.
Voice Chat is available in game as well as through many third-party tools (such as teamspeak3) that many players use to enhance communication while they are in a flight together (i.e. platoon, squad). The voice chat allows them to communicate more quickly and with more detail than using battle chat alone. Good players in a flight using voice chat can be an incredibly effective force! The level of coordination between those players can be far superior to anyone else in the match. However, the caveat here is that it is easy for the players in flight on voice chat to isolate themselves from the rest of their team - this makes their team vulnerable and the flight could easily find themselves outnumbered when the rest of their team is destroyed. When using voice chat with your flight-mates, always be sure to continue to communicate strategies and intentions with the rest of the players on your team.
Finally, the two biggest obstacles to keeping "well-ordered pennants" are: 1) silence/lack of communication, and 2) distracting spam/chatter. Try to keep these in check as much as possible - even minimal comms using the quick-key chat commands is far better than nothing at all, but too much can be more confusing than helpful. Finding the right balance is key and fortunately it doesn't take long to learn.