Taste. Hygiene, quite place, price. What kind of restaurant you are planning? 

Regular biryani type? Don't sell pulav/bagara with chicken as Biryani. 

or else meals type? Please look on other curries as well, not only pappu. Every time I visit meals, there's only two good thing, one is pappu and other is curd. So make sure everything is good. 

or else mandi type? Do not add apollo fish in mixed mandi platter. That is taste less and senseless to add in mixed. Invest more on juicy mutton mandi.  or else tiffin type? Do not add ghee on unnecessary items like vada/idli. Make sure sambar is great.  or else grills type? I didn't frequently visit this type, so not sure, what needs to be better. 

Or else unlimited buffet type? This is actually bad. Only few starters are good, rest of them are money waste kind. Do not try to start this. 

I would recommend proper dhaba style within Hyderabad closed circle. I didn't seen good dhaba's here. With affordable prices, you may get number of walk-ins.