You've gotten some really good tips here.
Only one that has me a bit
is serving out wide. I generally keep my serves up the T because I feel it's harder to return "down the line" and tends to set up my partner at the net with an easy/easier put-away.
Can't emphasize enough the need to both utilize and defend against the lob. And practice, practice, practice those overheads. You'll get a lot of them, certainly a lot more of them than in singles.
On the mental side, find the partner that "fits" -- one who won't jump on you for missing a shot and provide encouragement when needed...and a kick in the butt...when needed.
I've also found it easier to partner with someone who has a style in contrast
to mine. I'm quite aggressive at net...and find great comfort in a partner with a nice baseline game. Seems to work both ways since she says she is willing (and able) to hit groundstrokes all day...to set me up at the net. I'm still working on her to come in more...and she's trying to get me to hang back on occasion. It's a happy partnership.
Good luck and have fun with it. Don't take it...or yourself too seriously...and you'll do fine. And remember: be good and have fun...and if you can't be good...have FUN.