The first part in any spell...the intent of the working...is also the single most important part of the spell. The most poswerful invocations, intense energy-raising, time-honoured spell structures, or most carefully crafted components mean squat without the right intent.
While many might think that this is the simplest part of the spell...after all, it is the reason you're doing the working in the first place...it is also the part with the most room for errors. An intent that is too broad produces insufficient results, while one that is too restrictive can cut off avenues for the magick to work. Finding the right balance is important.
Be Specific!
The biggest problem that I see with many published spells is a lack of specificity in their wording. For example, if you want help in paying your bills, you might think that doing a spell to "get all of my bills paid" would be sufficient. However, this ignores the fact that magick tends to take the path of least resistance, and wording a spell as such might just lead to getting manditory overtime at work...sure, you get more money to pay your bills, but you have to work your behind off to get it! If you're OK with this, fine, but I try to make my magick work for me, not create work for me. Never mind the fact that such a broadly-worded spell might make old bills...ones you've forgotten about...re-surface and add to the list of demands on your resources.
If you want to do a spell to gain enough money to pay all of your bills without having to do more work than you're doing right now, then say so! Don't worry that your stated intent doesn't sound "cool"...there's a time an place for poetry, and it isn't here. The stated intent of a spell is a precice, technical set of instructions for the universe to delivier upon...as Issac Bonewitz once said, "warm, fuzzy magick produces warm, fuzzy results!"
Don't Micro-Manage
That being said, always focus on the end-result of the spell, not how you're going to get there. If you try to specify how a spell must be achieved, you muddy the waters and place roadblocks upon how it can be accomplished. Magick works through the path of least resistence, and it must follow it's own path, not yours.
For example, I tend to avoid money spells unless the only solution to a problem is money. If I have an electric bill hanging over my head that's past due, then OK, a money spell it is. Other results can be a bit more flexible, however.
Say you wanted to go to the Starwood festival next year. Some might try to do a spell for the money to pay to get in, but I would do a spell to "Go to Starwood 2008" instead. While that might result in extra money to pay to get in, it could also mean being booked as a workshop presenter (which is how I went), a musical act, a work-barter worker (who are vital to the success of the event), or a child-care worker (there is free child care during workshop times). You might find out that a friend is a vendor who's going, and needs you to come to help with their booth, and will pay your way in if you'll help (which is quite common). There are a bunch of ways to get to go, and if you only focus on extra money, you could be cutting off these other avenues.
Laurie Cabot tells the story of how, when her daughter wanted an expensive watch, she did a spell to get the watch, not the money to buy it. Right after the spell, Laurie did some psychic work for a corporation that gave her the exact kind of watch her daughter wanted as a thank-you gift for doing a great job for them. Thus, while the stated goals of a spell should be specific, don't extend that into telling the fates how the result sould be achieved.
Reach High
OK, this section isn't important for the technical skills of spellcrafting, but it covers a pet peeve of mine. When wielding the magickal forces of the universe, we are, in effect, using the same energy that the Gods used to create the universe and all that exists. It is an awesome, energizing experience.
It's not a time to be humble.
All too often, I have seen people scale down the magickal intent of a spell because they were afraid that their original goal "wasn't realistic". So, instead of doing a spell for a job doing something that they love, they do a spell to get a job that's "tolerable". Instead of doing a spell for bountiful prosperity, they do a spell to "make ends meet". Instead of doing a spell to find the love of their life, they do a spell to find "someone to spend time with".
Of course, it's easy to see why people fall prey to this. For most of us, our lives are based on humble returns. We've never had the dream upbringing, dream job, dream home, or dream car. Our culture drives into our skulls that we're not privilaged, and we should expect nothing more that what scraps the elie choose to toss our way...unless, of course, we buy the right perfume, clothes, car, television, etc...then we can be almost like the "cool" people! It's classic marketing...make people feel like they'll never be good enough, and you can use that lack of self-esteem to push products!
It's also classic class conciousness coming to light...since few people who resort to magick are part of the ruling class, most of us are people who are used to doing without. Living in a world where 2% of the population control over 80% of the wealth, most of us are raised with the feeling that we're lucky to have what we do, and we shouldn't push it (which is well-supported by the Christian establishment).
In magick, however, we should aim high. Don't do a spell to get a "better" job, do one to get your ideal job! Don't do a spell to move into a better apartment, do one to own your dream home! Granted, magick sometimes comes back in a less than ideal fashion...you may only get a better job than you have now, not your dream job. But if you never ask for something, it may never happen! Besides, it may appear that your spell has "only" produced a better job than you have now, instead of your ideal job, but it may just be a piece in a long puzzle that ultimately leads to the original intent.
Remember, you are a child of the Gods, wielding Their power...don't under-sell yourself!
Conclusion
When you first think of doing a spell, you're already performing it. Thus, nail down your specific intent early, and drill it over and over as you compose and implement the spell. It sets the stage for everything else.
Blessed Be,
Taliesin