You will also need a normal glue gun with some glue sticks. If you don't already own one, I bought mine at Wal-Mart for about $5 and I love it, it works great! Then of course, you will need your flowers. Most artificial flowers come in stems with more than one bloom though, some do come with a single bloom. Choose whichever you would like. You can use the multiple blooms to make clips for your friends or as gifts or spend a little more and get a single blossom with exquisite detail. Be sure to pay attention to the size of the bloom and be sure it is appropriate for the wearer. Some may not want to wear a huge peony in their hair while tiny cherry blossoms may get lost in anothers hair.
Once you have all of your supplies, take the blossom off of the stem. Position it on your clip or barrette to see where it best fits. Try turning it, adjusting and adding leaves to try and cover the barrette. You may even have to move the barrette off center from the blossom to cover it all of the way. Once you have figured out how you like it, put a line of hot glue down the metal clip. Place the blossom or leaf onto the glue. Glue anything else in place that you want on the clip. You may have to glue a petal or leaf down to fully cover the clip.
Get creative with your clips. Use a few of the same small flowers in different colors to add interest. Include a small leaf peaking out from under your flower. Maybe you want mostly greenery and only a small blossom on your clip. Add feathers of rhinestones to your flower to really bring some excitement! Instead of using hair barrettes use brooch pins (used on the back of pins, have a flat surface to attach something to) and add some interest to an old bag or bring life to a boring sweater or dress. Just get inspired and create something pretty (oh, so pretty).