I do hope your journal is somewhere close by. No? Well, go get it then, and I will wait.
Sit down with your journal. You can be alone or you can be in a crowd, but not watching TV or listening to music etc. Now, I want you to use your senses. All of them. Start writing. Don't analyse. What do you see? What do you hear? What do you feel? What can you smell? What can you taste?
To get going, you can start sentences like this...
I see dark wood table. I see black keyboard, with a light layer of dust. I hear passing cars. A bike just roared by. There is music coming from somewhere. Annoying music....
As you write, follow-on sentences will pour out. Let them. Follow your senses, and see where they take you.
Hearing and Sight are easy. What about others? How do your clothes feel against your skin? What about the chair you are sitting on? Is there a taste of coffee lingering in your mouth? What are you feeling? Enjoyment of dwelling deeper? Hungry? Bored?
Do this often, and not only it will improve your journal, but it will improve your participation in the world around you, and give you little surprises that so often go unnoticed.