Hi and welcome to SG
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Glad to hear you're enjoying I&A (Invade and Annex) I enjoy playing from time-to-time strategical with a group of boys.
Use teamspeak whenever, most members around the community start-up Teamspeak as soon as they boot up the computer, to either play with a few members, have a chat, or discuss issues / matters that need to be resolved with eachother. There's no set-times to be on and off from it, join whenever and go into any channel, members will either be in the channel or will eventually join depending on the time you're on.
To work as part as a time for I&A - Join the Teamspeak find the allocated channels for I&A (You'll live in them if you play I&A all the time). Talk and use your comms correctly, calling out directions, bearings, areas etc.. If you're a pilot get to know and coordinate correctly with your pilots. The other channels have the same rules applied, get to know them have a few chats etc most importantly do have fun.
The channels allocated for I&A are these (Be advised I have a custom skin for teamspeak, so your's wont look like this obviously.)
If you're unable to find these channels, just hit CRTL + F and type in "Invade" and it should pop up for you.
Over time you'll get to know people that play quite frequently and what not, you'll also make friends that's easy. I advise you to read up on the I&A rules (Here) so you don't get into trouble from any Mods / Admins on the server.
If you ever need help, feel free to join Teamspeak, find the Help-desk channels and any support member (Green, Red ticks / Mods & Admins) will help you with whatever question you have.
Best of luck,
Glad to hear you enjoy the I&A server AND most importantly have fun ♥