In Magickal rituals there is usually a structure. The deity of concept that is chosen to work with must be in harmony with the intended result or the ritual is likely to have unexpected effects. Most systems that are used in Magick have a wide range of concepts that encompass all desired purposes and part of the skill in constucting an effective ritual is in choosing the appropriate one.
Most Magickal rituals have several main parts; the banishing; the main ritual (including a statement of intent) and the closing of the temple. Although these stages are not all strictly neccessary, most people find that having some structure and a clear intent for the ritual makes concentration easier and leads to better and less muddled results.