Step 1: Proper Posture First
First, find some quiet time. This is very important. As much as I like listening to music while I work, this is my quiet time. Where I can work without being disturbed is equally important. You must be absolutely sure that you have at least a full day to practice the art because Alchemy can take many hours to complete
Second, find a comfortable place to sit. If you really cannot find a place to sit that doesn't make you feel comfy, don't even meditate then. A bed or even a foam mat will work.
Take a pillow and sit on it so your hips are forward and your back as straight as possible. If it helps, look slightly up. take each hand and lay your hands on top of each other and let your thumbs touch. This is a depth tracker. If your thumbs press too hard, you are too awake and must fall deeper. Too loose, and you are falling asleep. You must learn to hover just above sleep.
Here is a very good tutorial on how to meditate
Step 2: What Do I Focus On?
But a beginner should first learn to meditate and feel the flow of consciousness. Consciousness is what binds everything living together. But like a river, it flows and ebbs. Everything has a consciousness, even things we consider to be non-living, like metal. Some might think me crazy, but metal is just as alive as you or me. It grows and breathes. Albeit impossibly slow, but it does it none the less. One of the first things I meditated on was a tree outside my house. I felt it's heartbeat, it's radiating consciousness. It felt slow, but not as slow as metal. Living things, like my cat, are very quick and ever changing. Some might feel the consciousness differently, which isn't bad.
Be constantly looking and feeling the flow. In the future I will explain in greater detail what exactly consciousness is because I really over simplified it here. Just understand that consciousness is a very important thing to be in mind of.
Step 3: The Hardest Part
Now here is the difficult part. You must be able to keep your meditative state while moving and working. You must be void of all thoughts, emotions, memories, family and friends for the time you are working. Any kind of emotion and interaction while creating, say an elixir, must be kept at a minimum. This is the hardest part of Alchemy, keeping your emotions and keeping yourself in balance.