basically just chuck anything you want in it, add some herbs and stock and put it on low. Put it on in the morning and the food will be tender and delicious when you come home from work in the evening (some recipes do quicker esp if you put it on high)
The good thing about the slo cooker is that it doesn't matter if you leave it in for longer than you mean too. It doesn't really burn. I also thicken my food up with some arrowroot before serving (i'm gluten free so don't use casserole mixes)
When I was teaching, I had 3 slow cookers. I used to put the meat and veg in one, the potatoes in another and a pudding in the third. SOmething like rice pudding etc. When I collected my children from the child minders and came home, dinner was already and waiting for us, just as though mummy had been at home. Magic!
I have a 6 litre slow cooker now (larger family) and it is still my best thing. I use it everyday.