Dear Sir,
You should realize neither Okhla or Tuglakabad are official halts for this train. You say its better to deboard at Tuglakabad it seems as if the train always halts there.
I've qualified my tip with an 'if', you too can do the same.
I've...
more... travelled quite a few times by this train, and have seen it halt at Okhla almost every time, but not at Tuglakabad. If it does halt, its ok to get down there too, as the metro station is right near the Rly station.
Again, Okhla is closer to Nehru Place/Lajpat than Tuglakabad and its easier to get buses/autos etc from Okhla or Nehru Place than Tuglakabad.
:)