In addition to what's been already said, I'd like to add a few words.
I think a competent magical practitioner is far more about personality traits and disciplined living than they are about a skill set of techniques, although both are preferred.
* Personal development builds off of physical health, then emotional health, then psychic health. You can't skip around and have true, deep results.
For example, i see all this conversation about opening your third eye; well, there are five other chakras that come before your sixth chakra, ones that govern physical health, emotional health, your place in the world, how you give and receive love, and your soul's voice. All of these must be developed to some degree before jumping right in and attempting to "open" your third eye. People who are not firmly grounded in physical health and emotional health, often find instability when attempting to force open their psychic skills. Not that you have to be in perfect physical shape and perfect emotional tranqulity with no vices or weaknesses at all, it's just about not skipping the foundation.
You must grow roots before harvesting roses.
Having your basics learned, as Sue said, I'd focus on the following before casting a spell
~A quiet, non-reactive mind
~ Good physical and emotional health*
~ A sense of your own personal energy field
~ Creative visualization skills
~ Progressive relaxation techniques or similar
~ A daily spiritual practice, however you define it
~ A daily study period for reading and practicing magical techniques
~ Manipulation of your own personal energy field and other natural forms of energy
~ A security in your own personal power, breaking the habit of reliance on others and helplessness, personal accountability