planning to visit Australia in 2018

have you checked the time of year, weather wise for your trip. also the temperature/weather can vary greatly depending upon what part you are visiting. worth a quick check.

this topic 'may' have been covered before, suggest you do a search ( up the top of the screen)

http://www.australia.com/en

hope this helps

We travel independently in Australia, so do not have a recommendation from personal experience, but if you Google " active adventures Australia" a number of options will appear.

When comparing prices, make sure you understand if internal flights are included.

We've always traveled independently to Australia as well, and so can't comment on all-inclusive tour companies.
It might be a bit more cost-effective for you to organize your own itinerary to a few select locations and then book day trips from there. Trip Advisor has several options under their "things to do" pull-down menu for Sydney for example.
Sydney alone could keep you busy for a week, what with side trips to the Blue Mountains, the Hunter Valley, the beaches, as well as exploring the beautiful city itself via its excellent public transportation system. The ferries in particular are a real delight.
Also, if it's your first trip you need to understand how huge the country is, point being that you'll really need to prioritize in order to not spend all of your time transiting from place to place. It takes 3.5 hours to fly from Sydney to Uluru (Ayers Rock), and about 3 hours from Sydney to Cairns (the Great Barrier Reef).
JetStar is the low-cost airline within Australia, and their fares are attractive enough that you could easily string together a trip connecting (for example) Sydney - Uluru - Brisbane (or Cairns), giving you a good introduction to some of the highlights within the country, giving you your taste of the outback, and still not wearing you out in the process.
Doing your trip as an open jaw, ie flying into Sydney and returning from the last stop on your itinerary (Melbourne, Brisbane, etc.) would help maximize your limited time.

We just returned from a trip to Australia and New Zealand this morning. We planned it on our own. I had a friend of mine recommend AAT Kings as a tour operator but I like to set things up on my own. He said that they will work with you on any type of arrangements you want to make from a full guided tour to something along the lines of an RS My Way tour.

As FYI - We started our trip in Cairns for 4 nights. We did a Great Barrier Reef excursion with Quicksilver out of Port Douglas. We also rented a car for 3 days and went to Mossman Gorge/Daintree, Atherton Tablelands and Kuranda. We got to hold a koala at Hartley's Crocodile Adventures as well! Next up was Sydney for 4 days/5 nights which included a walking tour of Sydney and a trip to the Blue Mountains. The walk from Bondi Beach to Cogee is spectacular. We then flew to Christchurch (2 nights) and rented a car. We spent the next week driving to Queenstown (3 nights) with a stop at Aoraki Mount Cook for 2 nights. We took a day trip to Milford Sound from Queenstown as well. The last 2 days were spent in Auckland.

We loved Australia. It is easy to do on your own as other posters have indicated. Perth is worth a few days. I never saw the huge draw of Ayers Rock, but I suppose it is worth a stop.

Darwin has a lot of wildlife nearby and much of it is deadly. No swimming in that area. The crocs are huge. Cairns is a must see with the Great Barrier Reef and nearby rain forrest. and Skyrail.

Brisbane is a nice city, the Gold Coast is beautiful.

We spent five days in Sydney and loved it. We are going back to Australia next year and spending several days in Melbourne.

We enjoyed going on wine tours to the Hunter Valley and the Blue Mountains as well as an opera at the Opera House and a harbor cruise.

What do you mean by "back door" ?
With 2 weeks you would barely cover
Sydney - 4 nights
Uluru - 3 nights
Darwin & Kakadu - 3 nights
Cairns & GBR - 4 nights
Note that travel between all these places requires a lengthy flight as well. Hence, most tour operators offer modules that you 'mix n match'. Joining a tour group only becomes necessary if you make an overland joyrney, say down the east coast Cairns > Brisbane > Sydney > Melbourne. Avoid Nov to Apr if Uluru / Darwin & Kakadu / Cairns & GBR figure in your plans.

Don't miss Great Ocean Road when you are in Melbourne - the 12 Apostles scene was spectacular !

I would suggest doing thing independently in the cities, they are easy to get around and lots of good information to guide yourself. Maybe in the Centre (Uluru, King's Canyon, Olgas) you could look at a small group tours like those offered by: http://www.adventuretours.com.au/uluru-ayers-rock

And if you're wanting a really in-depth Great Barrier Reef experience I would highly recommend a cruise like this one: http://www.expeditioncruisespecialists.com/destinations/australia/gbrcc3

We've done this cruise and it was really great, you really feel like you see the reef and learn a lot too. It's not cheap and was a bit of a splurge but on the upside it did include just about everything apart from diving and alcohol.