There are many things one can do in preparation for a ritual. Of course, in times of emergency these steps may be overlooked, however the most effective rituals are usually those well planned and those you make plenty of time for.
If you can (medical reasons and circumstances aside) stop eating meat 48 hours before the designated time of the ritual. This helps to clear your body's energy fields from within, as animal flesh carries its own vibrations and is also simply harder for the body to digest. Again, if you can, 24 hour before the ritual eat nothing but bread, honey, and water. Be sure to drink plenty of water to avoid dehydration, the bread will help fill you up and together with the honey will give your body the simple sugars and carbohydrates it needs. You won't have a whole lot of energy and you may feel a little light on your feet, this is normal and desriable (but don't confuse lightness with dizziness! Fainting in Circle will not impress the gods or your friends, no matter how good you were at fasting!).
It is as important to be cleansed externally as well as internally, so take a good shower before the ritual. Wash your hair, shave, use plenty of soap. After the shower or right before the ritual, prepare yourself a ritual bath. The procedure for a simple purification bath is as follows:
Fill a tub with water and add the infusion. Step into the tub. Feel the impurities flow out of you. Inhale the scents of vervain. When the water has cooled, watch the impurities flow down the drain. Rinse the last drops from your body and step out of the water, knowing that you are now clean and ready for the ritual.
Sprinkle charged salt water around the perimeter of the room, being sure to get all the corners and even in the closets. Say:
Soft is the rain, it gently falls
Upon the fields beneath.
It lulls the heart, it stills the wind,
Gives solitude I seek.
It patters down, so gentle yet
It ne'er does bend a leaf,
And yet the water that is there
Will wash away all grief.
For smoothness follows in the wake,
And quiet and peace and love
Are all around in freshness new,
Come down from clouds above.
All evil go, flow out from here
And leave all fresh and plain.
Let negativity not come
Into this place again.
For love I now find all around,
So soft, so still, so sure;
I can perform my rituals
As peace and quiet endure.
(you can repeat with incense or a smudge stick if you like)