What makes a theory useful? Whether one is evaluating and investigating one's own or another's theory, there are some useful lessons to keep in mind. One lesson is that the reason a "good" theory should be testable, be coherent, be economical, be generalizable, and explain known findings is that all of these characteristics serve the primary function of a theory--to be generative of new ideas and new discoveries. Other lessons concern how to develop a theory (whether one's own or an adopted one). One lesson is to know what the theory is and what it is not--don't make it into something else either by "improving" it or by unfairly dismissing it. Know the theory's domain of applicability--do test its limits but don't overextend it. Know when the theory makes a prediction and when it does not--know when it is simply silent. This article concludes by offering the metaphor that the lessons for developing a theory to make it useful have a lot in common with good parenting. For example: Neither spoil nor abuse the theory; neither neglect nor abandon it; support and nurture the theory; don't overprotect it but do defend it; be patient with the theory--don't push it too hard or too fast; and finally, don't forget to love and enjoy it.