There has been a lot of interest lately in wicking beds. I got one last October and so far have been very happy with it, especially after the stinking hot summer we had. If you are going to put in raised beds I would recommend you look at a wicking bed. A wicking bed is incorporates a water reservoir beneath the soil layer. The plants are watered by the water from the reservoir being pulled up through the soil like a wick straight to the roots where it’s needed, helping to reduce water use.
I bought a recycled timber kit from Adelaide Hills farmer 2 Acre woods, but if you want to keep costs down there are number of do it yourself designs. See this Sustainable Garden Australia page for more information wicking beds and how to make your own. My one tip would be to take the time to level the ground you are putting the bed on. I didn’t and have noticed that the slightly higher side dries out more quickly.
Also see Costa’s How to make a Wicking Bed video: www.sbs.com.au/ondemand/video/l222662/backyard-revolution-how-to-ep3