Also, don't issue orders to Delta wing (or to "all fighters", which includes Delta wing). And don't order any ship to ignore the Lucifer. All of these will interfere with Delta wing's default mission orders.
By default, Delta 1 will go for reactor 1, Delta 2 for reactor 2, etc. Each will target reactor 5 next. If any Delta ship is destroyed, you'll have to take over for that ship, or order someone else to.
The best strategy I've found is to just keep the fighters away from Delta wing and let them do their work. Be aware that they don't start doing damage until several minutes into the mission, because it takes them a while to come into range.