Cats and kittens seriously love their cat trees.  They like to be up high where they can see everything that is happening in the house - the higher, the better.  Cats will appreciate their trees no matter where you place them, but the "best" spot would be in front of a window so they can watch nature when they arent sleeping in the sunlight.  I have multiple birdfeeders right outside one of the windows with a cat tree by it, and the cats and dog will spend hours there watching birds and squirrels.  A cat tree such as shown below can be found at pet stores such as PetSmart.   

             

Families with multiple cats will often find their cats lounging on their tree together.  I've noticed that when more than one cats are on a tree, they often have "their" spots.  In our living room, Junona always gets the top spot, her daughter Clairee will be on one of the ledges under her.  Clairee only sits on the top ledge when her mother isnt in the room.  The cat trees below which are positioned so the girls can see horses and other comings and goings on the farm are handmade by Cat Tree Kingdom in Illionis.  
                         

I recommend to pick a tree that has at least one area wrapped in sissel rope.  This will provide an "approved" area for your cat to scratch to their hearts desire.