Edging around flower beds is an important step to landscape design. Not only will it clearly define the edge of your flower bed, but it will also help hold mulch in the flower beds and help to keep grass from encroaching back into the beds as it grows.
Decide what you want your edge to look like. If there is an existing edge, you can follow along with that, but if not then you will have to design your edge yourself. Do this by laying twine along the ground in the shape of the bed until you decide how you want your edge to look. The twine can be spiked down and pulled tight to keep a nice straight line, or can be placed in a curved arc to mark off your edge. It can even be reused for multiple beds.
Make your preliminary edge. With a tile spade, go along your twine making small marks in the soil to set the shape of your edge firmly into the ground. These marks are simply small divots that will allow you to remove the twine and see where your new edge will be. There will now be a clear line in the ground for you to edge along.
Dig your edge. With a tile spade, go along your edge markings digging straight down a few inches deep and then pry the spade down lifting the dirt forward and out of the ground. Repeat this along your edge markings until you have created a vertical wall of soil defining the edge of the bed clearly. Step back and check your lines. If there are any jagged parts, you can smooth them out now and make sure you have clean, continuous lines.
Clean out your edge. Go along the edge, taking out the grass and loose dirt that you dug out. Make sure to pull any grass that still remains inside the edge near the soil wall you created. Now you can spray along the inside of the edge with weed killer or any herbicide to stop the grass from creeping back into the edge of the flower bed. This will leave you with a nice definition between the edge of your flower bed and your lawn.