I am a flower farmer not a floral designer, but I do love to play with flowers and have learned a few things along the way that may help you as you venture into flower arranging.
When putting together an assortment of flowers, you really want to have a nice balance of color and texture along with a bit of "pop". To achieve this, look at the arrangement as having five main ingredients: main flowers, secondary flowers, texture, fillers and greens.
Start with the main flowers and pick ones that inspire you. Think of this as your main performer, the ones that will shine. Then add the secondary roles, selecting what enhances the lead flowers but doesn't overwhelm. This is a cast of color and texture. Depending on what story you are trying to tell, it can be one color palette, similar colors or even opposite colors. As in a good play, they all have to work together. Add the textural elements and the fillers to make this work. Once you have all these selected, the greens will support and surround this cast of performers. So don't forget them! And don't just think "green", foliage comes in many different forms and shades. Look around at ferns, hostas, viburnum leaves, mint, rosemary, baptisia, geraniums and even the silver shades of artemisia and dusty miller. These are only a few and they will really show off your cast of characters.
Once you have your bucket of flowers and foliage, the fun part begins. Pick your container and start with your greens. Create the form of your arrangement, close knit or more free flowing. Then add some of your main flowers. Start placing the secondary flowers as well as some textural elements. The small details are saved for last. Experiment, use the same flowers, pick a different vessel and see what you can create.
With Youtube and Pinterest, there are plenty of places to find your inspiration and your style. Go pick some local flowers and play with flowers!
"Flowers always make people better, happier, and more helpful; they are sunshine, food and medicine to the mind." -Luther Burbank