The first question that should be asked is does the area need a bolted route. Many developed area's are non bolt friendly, that is they are primarily natural gear climbs with few or no bolt's. This should be respected and prior beta from the locals should be obtained before even considering bolting. Secondly, especially in established area's, you should make sure your next "mega classic", hasn't been climbed before using natural gear. The prior first ascentist might not take to kindly to your bolting their route.
To be on the safe side only bolt in areas considered sport route crags and even in these areas consider the area's rules in regards to type of bolts, lower off anchors etc and once again ask the locals as to the "rules of the crag".
When I bolt I try to find a crag that is new and has never been climbed before. In NSW, (I'm not sure about other states but it's probably similar), National Parks are generally no go zones in regards to climbing. Your best bet is to find some crown or state forest land as you are less likely to piss anybody off. Under no circumstances should you develop crag's on private property without first obtaining permission. Be courteous, just imagine if someone walked into your backyard and climbed your biggest tree just because it looked good?
To find potential crag's your best bet is to get some maps, topographic maps are the best, find where there is some spare land and go bush bashing. It can take some time, but you will be amazed at what you can find, even in area's supposedly heavily developed. For example, when I found Swamplands I had no idea that the Balkans was being developed just a few hundred metres away.
Finally, just remember to scope the area for possible conflicts later on. ie is the crag to close to houses, what are the land owner issues, does it really need bolts at all ? and of course once you find your new crag, post it on this website.