What not to put in a cot?

Could you please elaborate on the topic of "What not to put in a cot?" Specifically, I'm curious about the potential dangers or hazards that parents or caregivers should avoid placing in a baby's cot or crib. Are there any specific items that could pose a risk to the baby's safety, such as loose blankets, pillows, or stuffed animals? Additionally, are there any recommendations for creating a SAFE and comfortable sleeping environment for infants? Thank you for your insight.