depends on the size and stile of your desk. myself i like mini desks that are in staples. http://www.staples.com/Staples-Cormac-Computer-Cart-Maple/product_853580
you put the tower on the botom shelf. and then make sure if you have a usb back up drive it locked down so it cant fall over.
i like to place the power strip on the back of the lower shelf. use a wireless mouse and keyboard.
for printers i like these plastic or wood small stands.http://www.staples.com/Kantek-14-1-8-H-x-17-W-x-13-1-4/product_KTKPS510
if your printer is a wifi ink jet look to place it in the middle of the house so that anyone cant print to it.
with the pc if it in direct sunlight your dont going to see the screen well. also a night you want to have a nice lamp near the pc to keep down eye strain. I have cats there no real issue with fur in the case unless they sleep on top of the pc or rub it. with any good pc user if you blow the pc out once a year you wont have an issue. also a lot of new cases have screen that cover the power supply to keep dust and hair from getting sucked in. as a repair tech of pc i seen more pc with food or drinks spilled into them. a lot of new cases have 120mm or larger fans on top..people hit there soda and spill it into the fans and shorting out there system. if your going work and drink near the pc think about using a spill proff cup and put a cup holder on the side away from the pc. one thing with your pc make sure there no large power devices like an ac or fridge on the same line. when the compressor kick on you could have a brown out. also placement depends if you want pc connected by hard wire or wireless. if you want it connected to your modem hard wire you need to have it near your cable/verizion modem. a lot of people now using the newer 2 band 2.4/5g wifi and dongles.