I crate Bella at night when I go to bed, and I crate her when I am out of the house (for 3 to 4 hours max). I use a hard plastic pet carrier that is big enough for her to stand and turn around in, and put two soft baby blankets in the bottom for her comfort. She likes her crate, and will run inside when I say "crate!" At night, we put on the crate on the night stand so she can see us in the night if she wants to. If she needs to potty, she will wake us up in the night, but she can usually hold it for 7 hours (Bella is two years old now). This is the one we use:
NATURE'S MIRACLE Advanced Double Door Pet Suite Pet Carrier | Carriers | PetSmart
We use the 23" long X 15.25" wide X 13" high for Bella, who weighs 7 pounds.