I AM VERY NEW TO CAKE MAKING.... So all the cake recipes i have are to make 8 inch cakes... I have a cake that i want to use a 12 inch pan for... Do i just double the recipe, fill as usual and bake it for longer???
Do i bake for longer or will it burn?
Do I bake at lower temp?

I just dont know, so i figure, ask the experts!

Generally...and according to Wilton's Cake Baking And Serving Guides...
There are 3 cups of batter in one 8" round layer, 2" high.
There are 6 cups in one 10" layer and 7 1/2 cups in one 12" layer.

I'm no expert but you will indeed need to bake it for longer. I would also use a couple of flower nails in the middle to make sure the middle cooks properly too.

Measuring batteer by the cupful is SOOOOOOO messy!
An easier way to know how much batter is to fill *any* pan at least 1/2 full. That means if you are using a 2" deep pan, you pour batter in until you have at least 1" - can go as much as 1 1/2".

It looks to me like you are NOT in the United States (your screne name 'mum' indicates to me you might be in the UK). That can change things because your cake batter is different - most often, I take it, you use fruitcake.

A 12" pan will need about 1/2 again more batter - in other words 1 and 1/2 batters. It can take up to 1 hour to bake (mostlikely about 45 minutes) but does depend on the recipe used.
If you bake at a lower temp (like 25 degrees less) for a longer time you do not need a flower nail or anything else in the middle. I have baked many 100s of cakes without any and not had the center of the cake UNbaked. Having said that, if it gives you a feeling of calm then go ahead and use one 2 in a 12" cake is overkill

A traditional wedding cake may be fruitcake but we do bake an awful lot of other things other than fruitcake in the UK

I'm not sure what sort of cake the OP is making though.

Thanks everyone... I am in Australia, and I figured i would double the recipe (eg. mud cake) and fill the pan 1/2 to 3/4 full as usual, but i just don't want it to burn!!! I guess all i can do is try it out...