While preparing an excellent tutorial on some topic, make sure you are interested in it. It will not do you any good if you just randomly pick up any topic and start digging your mind. You must have a good grip on the topic in order to do justice to it. So always be selective when you are assigned the task of writing a tutorial.
Can you explain something to someone when there is a sharp noise coming from somewhere? Of course, you cannot convey your message to the other person well in the presence of a disturbance. Same goes for the writing that is ambiguous; it hinders the comprehension of the reader. He might find it difficult to grasp the accurate meaning of your words if they are not clear enough. So be careful about using words that truly reflect their meaning.
As you know a picture contains a message that is more pronounced than if explained simply in words. The reason is that our brain more readily captures things through images. It is imprinted in our memory and we tend to remember images more than the words. So, keeping in mind the significance of using images and pictures, make use of them within the text wherever possible.
Remember you are teaching, not dictating
You should not try to use harsh tone in the tutorial. Use a neutral instructive tone while giving tips on some aspect. You should not sound either too frank or too stern; be in the midway.
These simple ways can help you improve your tutorial writing skills to a good extent.