The use of magic is an integral part of Wicca. The involved process of casting spells includes gathering materials and adhering to fundamentals of the religion. Above all else, the Wiccan Rede thought of "an it harm none, do as thou wilt" (translation: do whatever you would like as long as it doesn't hurt anyone) must be heeded. Manipulating others or inflicting harm will be repaid three times according to the Law of Threefold Return.
Colors play a major part in magic and spell casting whether they appear in altar cloths, clothing, candles, stones or tinted water. Each color has a different representation or power it can bring to a spell. Red is sexuality, courage and energy. Pink is romance, love, and affection. Yellow is confidence, creativity, and luck. Green represents wealth, growth and fertility. Blue is peace and protection. Other colors and meanings can be found online.
Herbs and oils are used in magic but caution must be expressed in handling them. Just because something comes from nature doesn't mean it's harmless. Wolfbane and Belladonna are just two examples of poisonous herbs. Many oils and herbs are also irritants or allergens. Protective gloves and caution need to be used to prevent any unfortunate accidents. You want to make magic happen, not an emergency.
Stones and crystals are the most portable ritual item in magic. A spell can be placed on one or a collection of stones and placed in a bag to be carried with you. The scent of herbs and oils might draw attention but stones (hopefully) are odor free. Pentagrams are also wearable but if you aren't able to due to work or school rules, a traditional star like children draw still has five points. It is an acceptable alternative.
Before beginning a spell casting ritual, it is important to realize what the true nature of the spell is. A love spell, for example, does not make that person you're yearning for suddenly fall head over heels in love with you. That would be a violation of the Wiccan Rede since it is a manipulation. A love spell makes the caster more open to the idea of love and more capable of expressing it. Through changing yourself you can change what is brought unto you by the world.
It is going to be difficult to cast a magic spell without an actual written spell. If you are already a member of a coven that has a Book of Shadows, then you probably wouldn't need to be reading this. Individuals can find some basic spells online or in publications at New Age bookstores. Chat up those who have been practicing Wicca for some time for some advice and they may share a few of their spells if you seem genuine.
The difficulty of the spell is going to depend largely on what kind of magic needs to be done. For minor magic (like asking for luck) a few ingredients and a short often rhyming phrase will suffice. Larger spells may require the help of a coven who can assist you make a stronger calling on the four elements.