The basic rule of thumb is to have three sets of towels each (6 total): one hanging in the bathroom, one in the linen closet and one in the laundry. A set consists of a bath towel, a hand towel, and a washcloth. It's popular to monogram your towels and to mix and match color sets.
What are some other bath items I should consider registering for?
Other desirable items include:
Tub mat
Shower curtain
Accessories
Bath rug
If you are also furnishing a guest bath, you may want to include extra sets of bath linens, plus linen hand towels. If you like, you may want to add your monogram to the guest towels.