Where to start ...

1.) What should I do first?

you should RESEARCH first because you need to have a background or knowledge before you do something about witchcraft. What will I research? that depends on you, You might want to search first about crystals, herbs, candle spells, wicca, or even history about witchcraft -- it depends on what you wanted to study FIRST because we all have different paths and also you don't need to rush things out because you'll be taking it STEP BY STEP anyways.

2.) Other than researching what can I do as a beginner?

Practice MEDITATION because it is the best way to strengthen the mind because the most important tool for witchcraft is not the cauldron, nor the candle, nor is it even the spellbook (though they are just all to help you focus and borrow their energy) -- but its the MIND that can have the ability to manipulate energy (raising, holding, releasing, directing). One of the benefits of meditation is that it teaches you to compartmentalize thoughts and emotions so the ones you dont want, wont pop up at the wrong times. When youre spell casting, you are protecting your will in the form of energy forward a goal, imagine that energy like a laser -- the more FOCUSED the beam, the more powerful it is. Self doubt or emotions that are not conductive to that energy act like a diffuse, they weaken and scatter the energy you're trying to direct.

3.) What should I learn before I cast a spell?

Just like what I said, RESEARCH about the tools that you're going to use because candles, herbs, crystals, etc. have different properties which are associated with certain intangible qualities or events, like love, luck, and wealth. Thus, utilizing these correspondences reinforces the PARTICULAR INTENTION of the spell. What you should also learn is about a.) GROUNDING AND CENTERING (reinforcing your connection to the Earth and to yourself, bringing your energy into focus to help you feel more balanced.), b.) CLEANSING (cleansing yourself and smudging a space where you will be doing your spell casting so that the negative and positive energy will be detached to yourself), c.) PROTECTION (protecting yourself from evil 'stuffs')