A convenient way to get to Tughlakabad Fort is to get off at Saket metro station and to take an auto rickshaw from there. You can get one for Rupees 70-100 depending on how hard you can bargain. Tughlakabad is an imperial but tottering site. It reminds one of the power of the Delhi Sultans.
http://chandleur.wordpress.com/2014/07/04/tughlakabad-time-toll-tale/