Generally, most spells should rhyme as per part of the Wiccan Rede ("To bind the spell well every time, let the spell be said in rhyme"). It's not required, but it helps you remember your lines. It's also a good idea to actually write the spell down, for two reasons: (A) If you DO forget what you wanted to say, you can read it off the paper. I've done it, there's no shame in it ('less you're being watched by non-Witches). (B) Burning it in a special dish either during or just after the Working part of the ritual is believed to have a positive effect on the spell as a whole. It's usually a good idea to scatter the ashes (OUTSIDE!!!) instead of just throwing them in the trash can.
The reason for casting the circle is so malevolent astral entities can't interfere with you, and also being inside the circle brings you closer to the Divinity. I think.
Calling the Quarters does two things as well: It provides spiritual witnesses to your ritual and guards the circle from unwanted attention/evil/negativity.
The rhyme you use here can be used for every ritual you do, and as such should be fairly personal (in my opinion).
"As I light this candle mine, with X [God/dess] I align."
Say what works for YOU.
The next part after you've aligned yourself is the Statement of Intent. A couple sentantces, preferably rhymed, that tell the Goddess your overall purpose for coming to her tonight. Keep it simple, you don't get complicated until the NEXT part.
Now, for the actual Working. Here you say what you want in detail, and sew up any poppets, burn any paper, ring any bells, mix any herbs, or whatever you have planned to do. Power should be focused comepletly on your intent.
Now that you've thanked (thunk?) the God/dess(es), you'll want to meditate. Sit down in a fairly comfy position, close your eyes, and clear your mind. You might want to recite a mantra. Why meditate? So your mind is open for any gifts the God/dess(es) might give you, even if you just asked for your great-grandmother to get well. You should only meditate so long as you feel like you should. At some point you'll say to yourself "I should get up now." Do so.
Finally, close the circle (described on the other page) and clean up the area, moving furniture back into its original position if you're me. Then go raid the fridge, preferably for something high in carbos. If you have any excess energy, ground it, or channel it into your athame/candles/whatnot to give them a little extra boost.
And you're all done!!