Start by writing what you know! Whether it's technical, crafty or if you want to share how to raise chickens. If you write what you know the writing will flow much easier than trying to research an idea you know nothing about. In this way you can share insights that the next person may not know.
Follow all the guidelines for a stellar hub in the help center and make sure the grammar and punctuation are correct to the best of your abilities.
Read as many hubs as you can to get an idea of what is needed.