One of the very best parts of my job is being a tiny part of a new baby story, and working with momma's-to-be all day (and a few dads too!). I've been doing this for awhile now and something interesting I have noticed along the way is this: first time mom's are always apologizing that they don't know what they're doing, or don't know how many sheets they need, or even what a minky blanket is.
Ladies, don't be embarrassed!
Why would you know these things? Sure, some of us grew up with younger siblings or relatives around, but not everyone. I'm pretty sure our son was the first baby my husband ever held, and definitely the first diaper changed (or was that our daughter three years later? LOL and totally kidding, he's Super Daddy).
On the Crib
Sheets: Generally speaking cribs only feature a fitted crib sheet. I will say, a lot of my international clients like flat sheets, but in the US that is not very common. You want to look for something that can be washed A LOT, and features elastic all the way around to prevent the sheet from coming off while baby is sleeping.