Post lunch, head to the Qutub Shahi Tombs. The tombs are't very far from Tolichowki and an autorickshaw or OLA will take you there. This is a majestic place! Some of the tombs and the baoli are undergoing renovation. Look closely and you'll still manage to find the intricate stone work and carvings. Do visit the tiny museum; it provides a great perspective of how the architecture evolved and history associated with the place. From the Qutub Shahi Tombs head to the Golkonda Fort. Here again I advise you to take a professional guide. The fort is mostly in ruins, hence you won't appreciate the grandeur of the place unless you are shown around. Do climb to the top of the fort and you'll be greeted by a panoramic view of the city skyline. Stay back for the light and sound show. If you feel a trip to Hyderabad is incomplete without a visit to Paradise, the place famous for Hyderabadi Biriyani, do visit one.
My personal recommendation will be to visit the Jewel of Nizam restaurant at the outskirts of the city. Do make a reservation for this place and also arrange for a car to take you and get you back from there. In case the Jewel of Nizam doesn't work out for you, then I suggest Kabul Darbar for some authentic Afghan fare. If you want vegetarian stuff, head to Chutneys or Bikanerwala.You can also plan Saturday a bit differently starting with Hussain Sagar. Follow it up with Salarjung, Lunch Break, Chowmahalla, Mecca Masjid and finally Charminar. This way you can also get to shop at Laad Bazaar and capture the Charminar at night. Whatever suits you!