it can be a simple as a chant, or it could include items. so long as you but energy into it and focused on the spell it can work. feeling sleepy after is a sign you did put your energy into the spell, just be careful as it could of been the energy your body needs. relying on this energy instead of the energy all around us can result in you getting sick.
it is believed by many that the moon can effect spells, so if you cast by the moon i wouldn't recommend recasting the spell at this point. as the moon grows larger during its waxing phase [new to full] spells are cast for a positive manner hoping to draw these things towards us. the peak for these spells being on the full moon. if you are sending things away from you, then its the waning moon you should cast during with the peak being the new moon. if your spell was to draw love to you, starting on the full moon and recasting while the moon wanes might result in pushing love away. you can cast against the moon, but you'll be working against the natural flow of energy.
'feeding' a spell could be any number of things, recasting on consecutaive nights using the same candle, herbs, honey jar, amulet, whatever, can give more power to the spell. at this point, unless you wish to cast against the moon, i suggest putting things in motion. if you're going after a specific person, try talking with them, get to know them. if its a new love, go to social events, spend your time places you like but also where people would be. strike up conversations with people you feel drawn to. the universe won't make mr. right appear before you after the spell, but they will push the two of you into the same room. its up to you to talk to him [or her] just be open and patient. if after one moon cycle you have done all this and no one new has come into your life as a result, try again.