To get around visiting the temples, you have a few options. You can ride on the back of a motorbike or hire either a tuk tuk or car with driver. The back of a motorbike is cheap and looks like it gives a good adrenalin kick but comfort and safety... not so sure. A car of course offers all the comforts of home but that's also it's drawback - it offers all the comforts of home.
The fun of the tuk tuk
I found the tuk tuk to be the perfect combination. You can sit and
stretch out, you're protected from the sun, with the flaps down protected from the rain, you get a great breeze as you zip along, with a good driver you feel safe (although there are inevitably a few mildly 'harrowing' moments regardless of how you get about) and the ride is comfortable enough. The maximum speed they can go - given the small engine and road conditions - is slow enough that you can take in the cool stuff as you drive along but fast enough to cover a surprising amount of ground in a day.
Airport and bus pick-up and drop-off

Rate to and from Siem Reap area hotels is $5 for the airport and $3 for bus. For pick-ups, Savuth will greet you with a sign. If you tour two full days, Savuth will be glad to offer you complimentary airport transfer when you leave.
Touring the temples, Tonle Sap and other area attractions
Rates begin at $13 for touring the temples closer to Siem Reap ($13 for 'small circuit' and $15 for 'grand circuit'). This includes Angkor Wat, Angkor Thom, Ta Phrom, P
reah Khan and many other temples in that area.
Touring that includes the small or grand circuit combined with the lovely small temple Banteay Srei which is 35 km from Siem Reap, will cost between $23 - $25 depending on the exact sites to be visited. From Banteay Srei you can even venture a bit further to Kbal Spean (1000 Lingas) for only $5 more.
You can download the complete price list here: PRICELIST
The rates quoted here are pretty standard. Some fancy hotels may ask a bit more and some backpacker places perhaps a bit less. But, please note, when hiring a driver through your hotel or guesthouse, the driver loses a major portion of his modest earnings as commission. The high cost of petrol in general and the general cost of living in Cambodia at the moment is also a factor.
Customizing your schedule

My experience was, even after all my pre-trip planning, that in the end it's best to sit down with Savuth once you arrive and make the planning. Let him know what you're interested in seeing and how much time you have. In that way you can decide together what the optimal itinerary is to cover the most ground in your desired tempo. Savuth knows of course which temples are crowded when and where you can be for sunrise and sunset.