Hi Grantmac - I'm sure many people have different methods, but for me it involves spending a heap of time looking over maps! I'm not sure if you know about it, but there is a free online version of the topographic maps (for NSW only but if note that is where you are from) which also has satellite imagery. It's called SIX Viewer and can be accessed via
http://maps.six.nsw.gov.au/I find it a great tool for exploring new areas that look interesting, or for following along trip reports / track notes that can be found on the web. Some resources besides this forum (where you can search through it to find things already posted, or ask questions on an area in your own new thread which someone will usually be able to answer) include websites such as WildWalks.com and bushwalkingnsw.com as well as guide books on the area of interest which sometimes be found at a local library or bought through a bookshop.
If you are having troubles working out how far you should be walking in a day, or where are good spots to camp etc, then I suggest sticking to the recommendations of the above websites, or to what is given in trip reports (as long as you are of a similar ability to those who have done the walk before you).
I always record how long it takes me to travel each section of a bush walk, and over time you gain an understanding as to how fast you can comfortable travel within a certain amount of time. Generally 4-5km/h for good fire trail, 3-4km/h for good walking track, and slower speeds as the terrain becomes harder. A tool called Nasmithis Rule can sometimes come in handy for estimating speeds.
http://www.wildwalks.com/bushcraft/tech ... -time.htmlHaving a conversation with people who have previously done a route that you are looking into, or have covered similar area is always very beneficial as well.
What ever you do, don't be afraid to ask question on the forum, or to even post what your plans are before heading out for a walk. People here are always happy to give advice, some of which can be very helpful!