Buy the best you can afford and think of them as a cost per use investment. I would also carefully select a timeless design; nobody wants to offer their brother-in-law a pink leopard print bed in which to sleep.
Some people prefer to sleep on their back with their head high off the bed, others prefer face down in a small pile of down. I think offering a standard pillow and a euro pillow, like in the above picture, allows for customization and a great nights sleep. There are few things worse than waking up with a sore neck and a well rested guest will make your own day brighter too!
3. Thin Blanket
These are often referred to as coverlets. In the above picture it is the striped blanket. If you were at my in-laws it would be some darling quilted matelasse. I love a thin blanket. Even in the warmest summer night I want a little weight to my blanket, a very little weight. If your husband happens to be the temperature of the sun this might be all you need year round.
4. Thick Blanket
Duvets! I prefer mine folded at the end of the bed, just like in the picture. Sometimes I only need my feet to be nice and toasty, but on cold New England nights there is nothing better than pulling a thick down comforter up to your neck.
5. Too Many
If it's taking your visitors minutes to make room for themselves on your guest bed you, my friend, have too many pillows. If you need convincing of the hazards of too many pillows click here!
6. Too Personal?
The guest bed is not the place to display your stuffed animal collection from middle school. I don't want to fall asleep thinking about who slept in a bed before me. I like a certain amount of neutrality to guest bedding, think of a nice hotel and you'll catch my drift.
7. I have always wanted to invest in a bedside carafe. I think this one below is particularly lovely, but it'll cost you.