When I define a new pattern, sometimes all I get is a blank white box. Other times I get a border around my pattern that I don’t want. What am I forgetting?
To ensure that your artwork actually becomes part of the pattern, make sure that the objects are selected (and grouping them is a good idea) before choosing Edit, Define Pattern. To avoid an unintended box around your pattern, check that your bounding box has a stroke (and fill) of None.