here in the US,it seems the best way is to monitor dealers,ebay,etc-if it is not vintage, you just end up weighing what you are willing to spend vs. price brand new-if I had a LP Standard, I KNOW I could get more than 1000 USD for it...once again,tops do matter-if it has some nice flame,it will bring more $$ than a plain top/faded top...I have noticed faded tops going for 14-1500 USD on the Bay-I have bought a few from the bay..it is scary,but a quality seller makes all the difference-being a lefty,my choices are few-if I was righty, I would go pull one off a wall and go from there-if you can play it first,by all means do---the best advice is patience...wait for what you want-it will come!!
my next target is a standard in amber burst..AAA top..might take a few years,but hopefully I have a few years left..
also, check out some gibson message boards-best place to look for more advice