The best way to line a baking tin in my opinion is the following method, it is simple, clean and precise. It leaves for a clean edge and easy to take out the cake from the tin (perfect for those gooey brownies which you want just a little undercooked)
1. Pull the greaseproof paper so there is a good inch and a half over the tin then cut.
2. Have the paper curling up the tin and lightly draw around the baking tin in middle of paper.
3. Turn the paper over and fold on the lines, scoring with your nails for a clean edge
4. Cut into each corner leaving ½ cm each side, add a small snip into the middle for extra give.
5. Grease the tin, base and sides with the excess paper
6. Place the paper in and press down to corners, if required use a little of the buttered paper to stick the flaps down
7. Then fold the paper over the tin and score with your nails for a clean edge