My older yorkie, Lily, was crate trained before we got her, so she's been used to it already We're pretty much starting fresh with our 5 mo old, Bree.
At night, what really helps us is to put a blanket over the crate so the light doesn't keep them awake. Of course, at night it's dark anyway, but in the morning (esp early morning) this helps a LOT. Our 5 mo old whined, howled and barked a lot for the first week, but we don't respond to it that much other than a few 'SH's' here or there if any. After awhile, they realize they're not coming out and just stop doing it. Bree still will bark a little, but we just started this a couple weeks ago so we're getting there.
We just started in the crates during the day while we're at work. It's really been helping for potty training since they don't like to mess in their crates. We don't put blankets on them during the day, but my husband does come home on his lunch to let them out. We don't like leaving them in there for too many hours at a time. We aren't here to hear Bree bark about being in there, so what we can't hear, doesn't bother us.
Good luck!
