Make sure to use the non-stick type of bundt tin (some older ones may not be non-stick), grease the tin thoroughly and dust it with flour. Some sources do not recommend using butter to grease bundt tins with, but I personally never had an issue with it. You can also use non-stick vegetable oil spray or melted shortening instead. If your pan is particularly intricate in its design, use a pastry brush and melted butter/ shortening to get to all the nooks and crannies. Read this helpful article on How to prevent Bundt cakes from sticking for more tips!