Looking out the window: Although we may not all have the amazing views of the above home office, facing a window lets us expand our field of view beyond our tiny home offices and dream of fresh air and the outdoors. You'll see people, birds, animals, anything to keep us distracted from actually having to do dreaded work while at home. You'll have to be okay with leaving your back to the door so if you're not keen on someone walking in while you're browsing the web, this might not be the spot for you.
Facing the wall: This is probably the least favorite option but when you don't have a choice you do what you have to do. Facing the wall takes up the least room, is easy to place furniture, and the mess of all your tech is hidden up against the wall.
Facing the room Facing out also gives you the best view of anything and everything going on in the room and what's coming and going outside the doors and windows. If you have a window behind you though it might cause glare on your monitor, but they do sell anti-glare matte screens to combat this problem.
Caddy corner: I personally can't stand caddy corner furniture, but sometimes your space just doesn't leave you with much option. Or if you're into the look, it's a great way to change up the dynamic of a boring room and layout. There are even desks specifically made to tuck into the corner to take advantage of that otherwise wasted space in the corner.
Standing: No matter your orientation, a standing desk is a healthy idea that keeps you off your butt. Productivity (Images; Shutterstock/photobank.ch, Shutterstock/yuyangc, Flickr member jgarber licensed for use under Creative Commons, Clark Street Home)