Most important for your guest is the bed and bedding. Offer a choice of pillows and high quality sheets. For high quality and low price try shopping for these items at Marshalls or TJ Maxx. If your guest must sleep on a pullout or inflatable bed, provide a featherbed for additional comfort.
Provide an extra blanket and throw to keep your guest cozy and warm. In summer, have a fan in the room to keep guests cool.
Be sure to clear space in closets and dresser for guests to unpack and store clothes. Supply a variety of hangers for coats, pants, skirts and shirts.
Be thoughtful and furnish toiletries. Include basic such as toothpaste and towels as well as haircare items and body wash and lotion.
A fluffy robe is a pleasant addition to a guest room, eliminating the need for a guest to pack their own and take up valuable space in the suitcase.
A clock is a necessity and one that allows guest to play their music is a pleasure.
Some bedside niceties would be a water carafe, chocolates, reading material, a candle and a few simple flowers in a vase. A local paper, guide book or map would be helpful for guests as well.
I've found it helpful to spend a night in my guest room to see if it was comfortable and supplied all the necessary accoutrements to make a guest feel at home.