Alas, there is no simple answer to this question, because there are so many different types of magical spells.
Also, what seems a very easy spell to one person -- say, for instance, purchasing $20.00 worth of herbs, roots, and oils to prepare a love-drawing bath -- may be next to impossible to another person, due to a lack of dunds, an allergic reaction to certain herbs, or living in an apartment with no bath tub!
Some spells are quite elaborate and exacting, to be sure. For instance, there are candle rituals and personal empowerment spells that take up to 21 days to complete, working for a specific period every day.
But for every spell of that type, the knowing practitioner can cite a much simpler way of working toward the same goal, by lighting a prayer lamp, for example, or use anointing oil.
The best advice i can give to people who are curious about spells is this: Read about them, including on line, and become familiar with the tools and methods utilized in the spell-craft of various traditions. Try to visualize doing the spells, performing a mental "walk-through," as if studying for a role on stage or preparing for a social engagement.
Then begin small, with a request for something you want, but which is not a matter of life and death to you if you don't get it.
Don't wait until a horrible crisis time impinges on your life to begin praying for success -- start now, by asking for small but significant changes to occur.
Begin with cleansing baths and abundance work, drawing in blessings and the good things of life. Then, if you like the work and have success at it, you will be prepared and will be familiar with many of the supplies, tools, and techniques you will need when an emergency strikes, as well as having practical knowledge of how to use them.