The airport is very close to Yas Island - the driver should take the road which runs from the airport, past Masdar and Presidential Flights and then takes the tunnel under the road - he should not go up the main Dubai Road and then come off as that is the long way round.
The journey should be around 15/20 minutes and would be around 35-40AED - more if you arrive at night. All taxis have meters so ensure that they switch it on. Just make sure that you get a taxi and not one of the airport limos. If there isnt a taxi waiting when you come out, then call 600535353 and order one.
For tipping I would round it up but I dont add on 10%. So if the far was 28AED I would give 30AED, but if the driver has helped lug bags into/out of the car, then I would add more. Usually depends on what notes/cash I have in my purse!!
Just remember that Abu Dhabi doesnt really have street addresses so you will need to know a local landmark or building such as "back of Marks and Spencer", "Honda Building" etc. over 7 years ago