Crafting the perfect spell for your need can take some time and thought. A spell is more than just wanting something and wishing it so. The words you choose have meaning and you need to choose them wisely. The saying "Be careful what you wish for" holds true with crafting spells. I prefer to do all of my spell work on a full moon because the energy at this time is strong, but everyone is different and you need to figure out which phase of the moon works best for you. Try doing a few spells on different phases of the moon and see how it turns out.
Before any magical workings, take some time a few days before to think and prepare for it. Really think about what it is that you want, and be specific. For example, if you are wishing for a new job, if you just do a spell to "get a new job" it might work, but everything else you want out of that job may not be what you were looking for. Sit down with a pen and paper, and write down everything you want out of that job, details are very important. Let’s say your list goes something like this:
new good job
not too far from home
stable work environment
Now that you have written down exactly what you want out of this new job, you can begin to craft the perfect spell. Some people don’t feel it’s necessary to rhyme your spells, I do for a couple of different reasons. First, sometimes when words rhyme, they can be easier to remember. Second, when reciting your spell and the words rhyme, you get into a rhythm and it really flows nicely. You don’t have to be a master poet to rhyme, just do the best you can. I am certainly not a poet, but all of my spells rhyme for the added benefit. Of course as with any magic, the most important thing is your intent, but everything else that goes along with it will just help your spell to stick. Also make sure that after every spell, you end it with some sort of closing that will lock the spell in. Like "So mote it be" or "And so it is", find your own, whatever feels comfortable to you.
Now that you have crafted your perfect spell, wait for the right time to do it. Make sure you do it on the phase of the moon that works best. If you wish to use crystals, incense or anything else to help your spell along it always helps. As always make sure and sage yourself and your area before doing any magic. Good luck on your spell crafting journey!