Relax. Energy doesn't flow well through tense muscles or a tense consciousness.
Control your breathing. (This will also help you relax.) remember to draw energy in when inhaling and send it out when exhaling. Energy follows the breath.
Focus your mind on what you are doing and don't let it wander to what you did today, what you are going to have for dinner, how work or school will be tomorrow, etc. Remember, where your awareness goes, your energy flows.
Casting your circle, or opening your temple, creates your own space, seperate from the rest of the Universe where you can do your work in. It's a very important tool. Treat it like it is, with care and respect, and you will have the best effects from it.
And most of all, HAVE FUN!