I had the worst times w/ crumbs when I started decorating. The first thing that really really really helped me was thinning my icing down, it was just too stiff and was pulling up cake as I spread it.
And then it got even better when I started using pan goop as I call it instead of spraying or oiling/flouring pans. You can buy the Wilton cake release but I just make my own, it's equal parts flour, oil, and shortening. I mix 1 cup shortening, add one cup oil, then one cup flour until it's nice and smooth and have a perfect sized little bowl I store it in next to my oil in the cupboard. Just spread a nice layer on your pans with a pastry brush and it makes a nice smooth surface for icing!
Hope some of our tips help you, good luck, you'll get it!!!