you could meditate i heard that helps. and also putting your energy into the spell and concentrating on what you want from the spell. theres other thigs aswell like moon phases the correct items for the spell etc.
First,meditate for at least half an hour. It passes quickly. This will help you concentrate on what your doing. Next, do a simple protection spell,one that involves only concentration and a chant. They're extremely easy,and it's always a good idea to have one.