Sydney is one of those cities I will always suggest people use as they first start out with international travel. It would probably be a close second to London, only because for US citizens, the flights to Australia is quite a long one. If you do brave the 15+ hour flight, then the rewards are well worth it. Australia quickly became a favorite of mine.
Sydney in particular is a stand out for the great food, easy transportation, and lots to do. My trip and likely most first time visitors, will start around Sydney Harbor and Circular Quay. Circular Quay is the major stop for each ferry, a large subway stop, and a big waterfront dining area. I ate at least 1 meal a day at Sydney Harbor and maybe repeated 1 place. Lots and lots of options available.
From Circular Quay, you can grab a ferry over to the Sydney Zoo on the other side of the harbor. There you will grab a bus to the top of the hill and descend through the zoo all the way back to the ferry stop. I've been to quite a few zoos and this was definitely up there in the top ones I've ever visited. The entire walk is full of fun creatures, some very native and some not as much. The entire time, your walk is backdropped by the city across the harbor and the Sydney Opera house which can be seen for almost everywhere in the zoo.
Back in downtown Sydney, there is no end to activities and sights to see. From Sydney Harbor Bridge, to the iconic Opera House, the waterfront is the logical place to start. Moving inland from there, museums abound and a bustling city emerges. Museum of Natural History to the Science and Technology museum, I found the educational scenes to be good, but not great. As for the art museum, this was quite well done with many famous painters and lots of great art to check out. The art museum is situated in the large downtown park, and is fairly easy to get to.
Looking for an evening dinner location? At the top of the Sydney Tower is a rotating observation deck and a very nice, though slightly expensive, restaurant. Over a meal, you'll get the chance to see the entire city as you slowly rotate around the tower. I found the food to be a little underwhelming for the very high price, but the drinks on offer were very good. It is certainly worth a visit for the amazing view.
While I barely scratched the surface of Sydney, it is a place that certainly warrants a return flight at some point. Award flights tend to be pretty sparse to Australia, but even on a paid ticket the destination is well worth it. Think about making it a top destination on your future travel list.