So, as you type in each word, others magically appear below in the menu. The more words you type yourself, the more chance that you're using a completely one off, original search, and so the suggestions trail off to nothing.
This tool is extremely useful for webmasters and bloggers because they can be sure that if a keyword search appears, a reasonable number of people type that in every month. So, if you include such keyword combinations in your page and blog post titles and write lots of good unique content that's relevant to them you've got a good chance of ranking fairly highly for such searches, and ones like them. Targeted traffic will then follow.
That said, it's not always that simple, because some keyword searches have massive volumes and therefore huge competition. And that information is not included next to the words. Still, if you apply a bit of intuition it's not hard to find some keyword combinations with strong potential.
You can get pretty creative and find your own way of using this drop down suggestion tool. It's great for helping you get geo-targeted Aussie traffic too. One thing that people often do is type a country, state or city name, then their main keyword (or vice versa). Depending on how popular those keywords are, Google will then suggest many related, oft-used searches.
For example, if you run an employment themed website you can type in "Australia+jobs" and you'll get many suggestions. You can sift through them for ideas. And even some of the resultant three word searches listed will throw up still more that you can target.
Of course it's doesn't always follow that those typing in local location names are from Australia. However you can be confident that many of them are. Keep going with this technique - even if you don't do further research into exactly how many people type those particular searches and how many websites and blogs are competing for them - and you're sure to have some success before too long. Remember that a few such traffic trickles can add up to a flood over a year or so.