A news feature is a story about something that is of particular interest to your audience. It should engage them, keep them listening, and perhaps inspire them to talk about it with others. It should also leave them with a sense of achievement, if appropriate.
You can use the same criteria for deciding whether or not your article should be a news story or a feature as you would for any other subject, but it is usually important to consider the fact that a feature will take up much more space than a standard, short-form news story and will therefore need to be that much more interesting to justify its length.
When choosing a topic for your story, remember that people like stories about other people and about things which affect them personally. If there is a human angle to the story you are telling, and it will appeal to your audience’s natural curiosity and their emotions, then you will be able to capture attention and hold it.
Similarly, stories which have an element of surprise are likely to capture the attention and imagination of your audience and help to hold it. Often you will need to add some background information in order to provide your audience with context for the story. This might include the history of a particular event or some historical background on your subject matter. Often this will be necessary if you are discussing a topic which is not well-known to your audience.