If anyone would ask you what are the two most important strokes in tennis, what would you say?
Probably what 90% say, the forehand and the backhand- wrong!
Although they are super important the most important are the serve and the return.
Why?, well if you cannot serve the game becomes even more difficult than it already is, and the same on the return.These are the two opening shots in a game.
And if we think in terms of doubles we need to practice these two strokes.

You can either try this with a friend using half a court, which is easier if you are new to this, or in a team practice with all four on one court using the two diagonals.

So in the above practice 1 v 3 and 2 v 4.
To start with 1 and 2 are the servers, 3 and 4 work on returns.
As long as the service is good then the point is played out, but only on your diagonal.I suggest you play 11 points and then change the server.
If it is a team practice I suggest keeping the scores in each 22 point match.After 1 has played 3, they can then play 2 and then 4.So all against all.
At the end of the practice add up the points to see who came 1st, 2nd etc.Maybe if you are a ladies morning squad you can make the loser buy the coffee, and mens evening squad, well ,dare I suggest a beer.

Things to think about for:
The server.
a) try to get as many first serves in as possible.
b) concentrate your serve to the red boxes in the diagram.By serving down the centre of the box you cut down the angle of the return.
c)If its a good serve why not follow it in, just remembering that if their are four on the court, go in down the centre of your half( which is of course correct in a real game)
d) as a server YOU have the first chance to get to the net so take it.

The receiver:
a) make the server play a second shot, even if its a bad return there is always the chance that they will make the mistake, give them that chance.
b) If the server starts to serve and volley, try to keep the returns low to force the low more defensive first volley.
c) If the server stays back you take the initiative to get to the net.

For both players remember, the furthur you are from the net the less angles there are, once up at the net a whole new world opens up.