Getting started with spell casting most importantly includes working with energy. Spells on their very basic form are energy manipulation for a significant goal. To get started with energy manipulation, you have to learn about the flow and keep using techniques and energy exercises. A very common technique of feeling your energy flow is a Psi ball which absolutely serves that very specific purpose. After that you keep working on energy manipulation and then you are able to do something with your energy as a casting. Many energy exercises can be found on and outside this site.
After getting familiar enough with energy manipulation you go over basic spell casting terminology (nobody said it is essential), such as; Ritual supplies and ingredients, Moon Phases, etc. These are indeed merely optional while it is worth going over those terms to widen your knowledge about spell work.
Finally, if you haven't gotten into it yet, it is important to have a certain level of concentration, focus and relaxation. These are achieved by practicing daily with the right methods. From here it is all up to you, there is nothing you can't look up.
Remember to use meditation to relax yourself and get familiar with energy.