Creating your own spells and rituals is an important step. Paganism embraces individuality and personal exploration. Your spells and practices should reflect that. There are many lovely rituals and spells available but a good Witch should be able to write their own. I read somewhere that using another's spell/ritual was like wearing someone else's underwear. Your own spells and rituals are tailored to your own needs and use of energy. Although a pre-made spell will work, spells and rituals created by your own hand will have better results.
Writing your own rituals and spells can be very fulfilling. It allows you total freedom to worship the God and Goddess the way you want. You can be assured that you can create a ritual or spell for all needs and times. Along with this freedom there does come responsibility!
If you create a spell or ritual, eventually you'll want to cast it. Well, have you thought about it? There are plenty of people who cast spells everyday. Some are Pagan and others are from a variety of different religions. Wicca believes that everything you do will return three times stronger. If you send out positive energy with your spells, eventually you will receive positive energy in response. This is true for negative energy too. So, before you cast that spell to give your enemy a boil in an uncomfortable place, think! Is it really worth it? Usually it isn't.
Ethics in spell creation are important considerations. Before any spell is created, you must think of the spell's implications. There really are just two rules for spellcrafting and they are to do no harm and to not remove someone's free will. Why should we magically remove another's free will or harm someone when mundanely those actions are considered a terrible crimes? It never ceases to amaze me how many people think it's okay to do a negative act magically that they'd consider wrong if committed mundanely. So, think before you put pen to paper!
Another thing to keep in mind is whether you really need to use magick. It's easy to start casting spells and conducting rituals for every little thing. Magick is powerful but it's not always necessary or the best alternative. Often spells work in unexpected ways. They can also work less promptly than we'd like or have interesting side affects. Magick can also make a situation more complicated. First brainstorm and work out mundane solutions to your problem. Generally it takes less time and less energy to follow through with the mundane solutions. Magick isn't a cure all. The caster has to take an active role.
For example, if you do a spell for prosperity, then don't expect money to appear in your wallet or purse. You shouldn't keep spending your money and doing the things you know are not conductive to prosperity. That just defeats the purpose of the spell. Instead create a situation that can take advantage of your spell. Nor should you think that because you did a spell that it will automatically work. There are many reasons why spells don't work. Even the most experienced of Wiccans cast spells that don't work. I believe that most of the time when a spell doesn't work that it is because we have to learn a lesson or that the spell wasn't needed. If you are ready to take on magick's responsibilities and accept its disadvantages, begin creating. It is a joyous experience to work with magick and to create the means to work with it. Just remember that it's also a force to be respected.