Basics – Yōsetsu

You will need the following inexpensive items in order to practice writing kanji with a brush.

Choose carefully where you are going to practice. You need to be able to concentrate and to write in comfort.
Although it is traditional in Japan to practice sho while kneeling at a low table, it is fine if you want to sit on a chair at a desk or a dining table.
It is important that your sitting or kneeling position is stable, so using a chair with casters is not recommended.
You need to be at a height which will allow you to move your arms freely, without being too far away from the table. Try to sit so that your navel is slightly lower than the surface of the table.
You also need to be close enough to the table so that you don’t have to stretch to write characters at the top of the page, but not so close that your arm ends up cramped against your chest when you write characters at the bottom. A good yardstick is to sit so that you can just fit your fist between your stomach and the edge of the table.
In order to write well, you need to maintain a good posture: face the table, straighten your back, and if you are sitting, place both feet flat on the floor.
Place your paper on your felt underlay so that it is slightly to the right of your body’s centre line and put a paperweight at the top of the page to hold it in place.
Place your left hand flat on the left edge of the paper to stop it moving around as you write.
You should write with your right elbow slightly raised, so that it is free to move. Don’t raise it too much, or your shoulder will soon start to ache.

Basic writing posture.

Holding your brush correctly will help you to write well. Hold it so that your index and middle fingers are in front of the brush, and your ring and little fingers are behind it. This way of holding the brush is known as sōkōhō (双鉤法) in Japanese. There are other ways, but I recommend this one, especially for writing kanji.
Your thumb should support the brush in such a way that you could fit an egg into the space in your hand. The middle joint of your index finger should be level with the center of the shaft.
Grip the brush firmly.

Brush grip.

As you focus on the characters you are writing, your posture and grip will probably get out of shape, so check how you are sitting and holding the brush from time to time and make any necessary adjustments.

Look at the shapes of the lines. The shapes of the start, middle, and end of each line will all be different, however subtly.
Look at the angles of the lines: Are they exactly horizontal or vertical? Or are they at a slight angle?
Look at the curvature of the lines. Are they dead straight? Or are they slightly bent? Look at the spaces between the lines. When you write, it is not just the black lines that are interesting, but also how they divide the white space on the page.
Put plenty of ink in your inkpot and load up your brush with ink. Wipe off any excess on the lip of the inkpot so that it does not drip on the paper. Refill your brush when it starts to run out of ink.
Keep your brush vertical so that you write with the tip. Writing with the sides of the brush produces weak-looking lines.
Don’t be timid when you write. Write with conviction and energy.