When you are playing level doubles and you are in an attacking formation, one of you at the back and one at the front. The player at the front should be for the most part in line with the rear player.
When smashing from one of the corners the front court player can take a step towards the centre of the court slightly using the tram lines to zone out replies outside of the reach. This is because 70%+ of all replies will be a straight lift or block because cross court replies are difficult if the smash is placed correctly.
Depending on the distance the rear court player is from the base line, as someone else mentioned already, the front court player should keep a roughly half court distance. If the rear player is on the baseline, the front court player should be behind the service line by a foot or two.
This is to give the front player, more time to intercept return shots because the steepness, angle and power of the smash will be less than a smash further up court.
When the rear court player is smashing at 3/4 court, the front player needs to be on the service line or just ahead of it because the replies will usually be weaker due to the reduced reaction time, faster smash speed and angle comg up rather than flat.
The front court player needs to have their racket up and ready at all times, looking for and hunting the shuttle coming back across the net. They need to try their best to be enough of a threat to cut out any flat fast shots cross court, reducing pressure on their partner, to pick up any block replies and intercept any straight drives.
There will be times when your opponents do manage that cross court block or find the right speed and height to whip it past the net player but if you are playing the front court well this will be far less often than it may be currently.
It is the rear court player's responsibility not to float any drops or smash too flat, which would put the front court player under pressure. Smashes and drops should be 90%, straight, at the body, or towards the centre line between the two defenders. Any smashes cross court open you up to a flat drive into the open space and immediately put you under pressure.
I'm Male and much prefer Mens doubles to mixed, primarily because the level of women in the section I am currently in is no where near strong enough from the rear court. I am strong from the back of the court but I feel my speciality is front court and net play. If i had a female partner who was confident and strong from the back, full length clears, good drops and good angled and placed smashes I would be more than happy to cover the front.
The only advantage men have at the back is slightly more power and slightly more agility. Of course this is only at the higher levels of play.
Rotation is more difficult and is a different thing to simply covering the front court properly.