Storytelling is really the most important thing but "tell a story" is hard advice to follow so I'm going to go for a simpler approach, you can think of a picture as having 3 parts:

1. The subject

   You should decide what the subject is and make sure it is the most prominent item in the image, you can make it prominent by making it brighter, more colorful or bigger (there are other methods, but those are the easy ones)

   For example in your photo the most prominent item is the window frame because that's the only item that's (partially) correctly exposed, everything else is dark.

   If you want the man to be the subject you need to make him properly exposed, asking him to move into the light for a minute is a good option, lighting him with a flash is another, both option would have made him bright and colorful on a dark and dull background.

2. Supporting objects

   If you have other objects in the background you have to make sure that 1) they are visible, 2) they don't take attention away from the subject and 3) they help you tell the story

   For example, a man with a typewriter suggests he his a writer, a man in a market (where it's recognizable as a market) suggest he is selling something - on the other hand, a man surrounded by random junk doesn't really tell us much, is he a some kind of a random junk collector? was there a freak accident that dropped lots of unrelated stuff on him?

3. Background

   Everything else is background, it's very important to take a good look at the background and make sure there's nothing there we don't want in the image.

   The only role of the background is to be invisible, you need to make sure there's absolutely nothing in the background that calls for attention and that the subject and supporting items are distinct from the background.

   A good background can improve the picture - but leave this for later - after you learn to make a background that doesn't hurt you can start working on making the background actually support the story.

And watch the light, always look at how the light looks before taking the picture, the light is an extremely important part of the photo - this is so important I just repeated it 3 times and I would repeat it even more if I had the time.