I have been asked a few times how I write a drabble. Some people find it difficult to write a 100 word long text in one try. Yes, it is! It takes a few steps, at least for me! So here they are! Hope this helps and encourages you to write!
Step 1 - Write, write, and write! Don’t worry about the length of the text. Create the main idea, the main characters and the plot. (My first version tends to be about 120 something words)
Step 2 - Cut, cut, cut! Now that you have had all this work, destroy it! Kidding! Just edit it down as much as possible; keep the core of the story. Hint some details; avoid stating the same content by describing the action and having a character say what is happening. Edit out adjectives and adverbs if needed. (The second draft usually goes down to 90 something words)
Step 3 - Add, here and there! Work on the flow of the story; rearrange the sentences and finish with an unexpected or funny or horrid or… ending! It’s a lot of fun trying to catch the reader off guard! (Success! After nipping and tucking here and there, the text is now 100 words long!)
This is just my method for writing a drabble. There are other approaches, I am sure! And I am also sure you'll find your own method as soon as you feel comfortable writing a very short text!