Prior to writing a note to the Western Wall online you should think about what is important for you and what you wish to thank your Creator for. Make only one petition in a note, but write about the dearest one. Do not ask God about something ordinary or common, if you know you can handle things on your own. Ask for strength in your soul and body to do what is right; ask for health and wellbeing for your dear ones. Do not wish any evil to your enemies in the Notes! Whatever you ask for, do it sincerely and openly.
There are no strict rules for filling the notes. You can write it in any way you like and on any language and of any volume.