We don't have a set "nap time" but she tends to nap at roughly the same times every day and I just watch for her to give me cues, but as soon as I pick her up and put her blankie on my shoulder she snuggles in and knows it's time for a nap. She gets her blankie, paci, teddy bear and sound machine... normally that's enough but she just wasn't taking to it. She just sat in there babbling for a while and then she started screaming.
Today she's back on schedule though, thank god!