Pakistans rickshaw transport is a double edged sword. They are incredibly easy to use and rarely exceed 40 rupees but the entire environment suffers at the hands of the fumes. They are great to use and are brilliant in getting around during the heat but the fumes burn your eyes and dry out your throat. Overall, fun and advantageous to use but pollution has beat some cities into submission.
Whenever you plan to take a taxi but make sure that your Taxi driver knows the place where you wish to go !
If you by chance think of travelling in 'Ricksaws' - The Three weelers then make sure that they don't drive fast. The are usually comparitively cheaper than Taxis but not as safe as Taxis are ! so, be careful about Richshaws.
In the big cities, the taxis are pretty easy to spot - they are the yellow and black painted small cars (usually little Suzukis) and are often well decorated both inside and out.
Transport in Pakistan is like art-on-wheels with the drivers taking such pride in their vehicles.
As for fares, I started using taxis in Islamabad but moved on to buses and minivans as they were sinificantly cheaper. There are no meters in Pakistani Taxis so I recommend finding out a little about average prices to get to points around the city. A lot of drivers will, upon requesting the fare reply with "As you wish" I found this hard to deal with as I knew that I would probably be paying an inflated fare anyway - just on account of my perception of taxi fares back home in Australia.
All in all, approach taxis with an air of fun and don't be afraid to bargain for fares.