Mitering is the most used method of corner-joining most kinds of trim. Now in case you're wondering what is mitering, just look at the corners of any wooden frames of doors or windows. Do you see the two pieces of wood joined together, with each piece of wood cut at an angle? Well, that's mitering. Now for an amateur, it may be easier to use corner blocks or rosettes. This allows you to save a lot of time and effort! Now these blocks tend to be thicker than the casing boards however, they don't need to fit perfectly against the blocks to look right. The key is to make sure that both the blocks and the casing ends are square. This will ensure that the joints are tight even if the casings are tipped a little in one direction or the other. Corner blocks can be made from wood stock or purchased as finished units in wood or plaster with decorative faces and can be found in hardware and moulding stores. Installing them is a breeze! Just butt the casing as you nail the blocks and the casing to the wall. You are definitely not going to want to put all of the effort into mitering after using this method, mitering corners will be a thing of the past!
You may also be interested in "Moulding End Caps- The Finishing Touch".