How can I make my answer featured?
You can't really make it featured yourself because there is a reviewer for each subject (You can find the list of reviewers here)
Then the computer randomly picks out answrs and sends it to the reviewer for that subject. Then the the reviewer looks through that queue of answers and features the best ones! (For more explanation about the queue, make sure you read this )
Like Stefan V. said, it goes without saying that a lot of answers that could be featured will go unnoticed, that's just the way the cookie crumbles. But even in such cases, the reward of writing a great answer lies in its long-term impact on helping students learn, not on whether or not it gets a trophy.
So you should continue to write great answers. Some will eventually get featured, some will not, but they will undoubtedly help students in the future → the name of the game! :D
Maybe, take a look at this! It might help you!
More info on featured answer here.
In essence, you must provide an answer that is easy to read, intelligent, well-thought out, instructive (most important part!), and (possibly) neatly-organized.
If you think one of your answers is capable of being "featured", don't get down if doesn't! There are plenty of people that can feature your answer, but unfortunately there are too many questions being answered (which is great, isn't it?), and there is a chance that it could be "swept away" with the flood, and it may get lost in the giant network of questions.
If you want to look at some featured answers, follow this link to get an idea of how contributors answer!