1.Where you cat spends his time?
Is he sitting at the window watching birds or playing with you in a living room? Or maybe he’s watching the washing machine in your laundry room? Having a post near where he spends reasonable amount of time seems quite logical.
Maybe you already figured it out, but your probably will need more than one scratching post in your house. Place them in strategically important places (as mentioned above) so your cat always has appropriate place to satisfy his needs. Your carpet and couch will be thankful!