Devotionals are ritual acts and meditations that are designed to focus your attention on a particular deity, group of deities or other spiritual beings (such as Ancestors or Elementals). These rituals express the connections between you and the Deities.
Through the process of these rituals you will discover things that the Deities, Ancestors and Elementals are associated with, what they like, and also the things that displease them and which you should avoid.
Reading and meditation are vitally important before you begin to design your devotional altar/shrines and/or your devotional rituals. Both are necessary and will give you the basics of symbolisms for setting up your devotional altar/shrines, and the names and some of the titles by which your chosen Deity/ies should be addressed.
Your research will reveal tales and material which can become the basis for the words of your devotional rites, as well as the conditions and situations in which each deity is most often encountered.
A devotional can of course be done with no props other than your intent, particularly when very little is known about a Deity, but using linking symbolism, if available, is always helpful.
Researching and preparing a devotional ritual shows the Deities that you are actively interested in interacting with them, and will call their attention to you in a positive manner.
Preparation is, however, no guarantee of success!
Time and effort are both important ingredients for devotional work. As with all spiritual work the nature and development is often slow and painstaking.
Success will undoubtedly come, but you must reach for it and put your best effort into your workings. Always remember that what you get out of your devotional rituals will be dependent upon what you put into them. Your effort may be great, but your rewards will be greater.