How can I improve my descriptive writing?

Good descriptive writing allows the reader to feel the story as you do. This may seem a daunting task at first, but taking a scene piece by piece can help you organise your thoughts. The more you understand about your own writing, the better you can describe it to your reader! Let's take a scenario where you may be asked to describe the setting:
A summer's day at the beach.
The first step is to break down the scene using the Rule of Fives.
The five Ws: Who? What? Where? When? Why?
And the five senses: Sight, Hearing, Smell, Taste, Touch
Answering these questions will not only walk you the process of your own narrative, but can keep you focused in your description.
Who? The first question is to ask yourself who is in this picture? How old are they? You may find it helpful to have a main character, such as an 8-year old visiting the beach with his grandparents. Perhaps you would like to give him a name as well. The more you know your character, the easier you'll find it to describe his interactions with the setting.
What? What is this boy doing? Is he playing in the sand? Does he have friends joining him? Ask yourself what actions are happening in this scene. Try and keep your answers short and concise. The idea is to show the reader what the characters are doing, instead of telling them. By keeping this part short, you'll find it harder to simply dictate what they're doing.
Where? While we do know this particular scene is happening on a summer's day at the beach, here is your chance to go into the main part of the detail. Start off by listing words that remind you of summer and a beach: hot, sand, sea, sun, sky, fun. Now take it step further - instead of telling the reader that it was a hot day, describe what happens to you when it gets hot. Your hair sticks to your neck, there's sweat on your forehead, your cheeks get all red and flushed. Take the words and try to pull the reader into experiencing the same emotions and feelings associated with each one. Top tip: can you write your responses without using the original words?
When? Ask yourself what time of day is your scene at. Is it at noon, when the sun is highest and thus, the hottest? Or perhaps in the late evening, when it is cooler and darker and the sky is shades of red and pink and blue? Similar to your response above, you want to show the reader what time it is. Use the colour of the sky and the temperature of the air to help you with this.
Why? Why are your characters at the beach? What made them decide to run into the sea instead of sitting on the sand? Questioning your character's reasoning behind their actions will help you describe not only what is happening in the picture, but the scenery that influenced your character's decision.
The Five Senses
While answering every W, write a sentence on each of the five senses. An example could be, while you're describing where the scene takes place, you could write about what you or your character sees (a bright sun with clear blue skies, your grandmother's red face), what you hear (laughter and chatter from a nearby volleyball game), what you smell (the salt from the sea), what you taste (your favourite BBQ chicken you had for lunch) and finally, what you feel (sweat on your forehead, warmth in your cheeks).
Try and do this with every question, and you'll soon have a very fleshed out plan for your writing! All you have to do now is piece your different phrases together to create a narrative. The more you practice, the quicker you'll be in writing all your responses.