I would not put anything frozen into a preheated crockpot. That can cause it to crack, especially with the newer ones because they heat up quicker and get hotter than the older ones.
American Scrapper.... most meal pre can be done the night before and then put into the pot in the AM.
Main things to remember to keep it safe is to place the corckpot in a safe place..... heat proof surface, with nothing with a certain distance of it (I think recomended is 8in, I would be safe and do a ft.). Keep it away from the edge of the counter/table etc. Do not let the cord drap off the surface. Have it plugged into a grounded outlet (even safer woudl be to used a surge protected power strip). Make certain pets can not get to it.