If u flick serve in doubles, try to make sure yr partner is ready or even signal him before u serve. Right after the serve you have to move back to yr serving side n yr partner should also move to the other empty side into a defensive position, expecting a smash return. But if yr partner is not ready then you will be in deep sh**t if yr opponent just tap-smash to the empty side because yr partner is not in defensive position yet
you and your partner should move to cover side by side together. who takes which side needs to be communicated between the two of you though....
I would always move to the same side you are serving from - you don't have much time, neither does your partner, so don't cut them up! The straight smash is the harder one to defend and your partner who is further back has the best chance of getting to it. Just take one step directly backwards and get ready to attack an shot hit down the middle (towards you!!!).