Taxis in Islamabad are abundant, popular and generally safe. Cost is around Rs70 - Rs100 per sector traveled, depending on your bargaining skills. Prices will be higher at night, especially departing from places like Jinnah Super F-7. It is always advisable to agree the fare before traveling.
Car Hire is also a good way of getting around. Although road signs and directions are only available on main roads, the city's grid and numbering system make it relatively easy to find your way around. There are various car hire companies in Blue Area F-6 and also in G-8 Markaz where cars can be hired with drivers. Most major hotels have their own car hire services and are relatively cheap. A tip to the driver at the end of the booking period is appreciated but not mandatory.