There are a few methods for writing these symbols. Today we'll start with the easiest method, which is learning the Japanese terms for symbols predefined in the default Windows conversion dictionary. (Was that a mouthful? I mean to say, "We'll tell you a bunch of the symbols you can write from your Japanese without having to do anything technical.")
This guide assumes you are using Windows as your operating system. However, the same icons should be available regardless of your operating system, as long as the font you are using supports them. Linux and Mac systems have character palettes, too, and their IMEs can be "taught" how to type these characters from defined keystrokes, too.
Anyway, on to the main course:
For starters, some of these symbols are already programmed into the Japanese IME.
If you type the word for "star" in Japanese, ほし, then push spacebar to convert it, you'll find that not only is the kanji for star, 星, available, but so are the icons ★ and ☆, among others.
Here is a list of some simple predefined symbols in Windows' IME dictionary.
Just typing the hiragana on the left should create the symbol(s) on the right!
|Type in:||To get these icons!|
|やじるし||↑ → ↓ ← ⇔ ⇒|
|ほし||☆ ★ ＊ ※|
|まる||● ○ ◎ ㊥ ㊨ ① etc.|
|しかく||■ ◆ □ ◇|
|さんかく||▲ ▼ △ ▽ ∴ ∵|
|おなじ||々 ゝ ゞ ヾ 〃|
|すうがく||＝ ≠ ± ∞ ∑ √ etc.|
|たんい||％ € ℃ ㌔ ㍍ ㎡ etc.|
|きごう||hundreds of symbols|
This list is not comprehensive, by the way. There are dozens of other words recorded into the default Windows IME dictionary and linked to symbols as well as kanji. This is just a taste of some interesting or useful commands. Here is one much more comprehensive (and overwhelming) list of symbols for those interested.
And, as mentioned before, if you aren't using Windows, or if you are using a different version of Windows (this list is current for Vista and 7, using the Office IME 2007), some of the words here may not produce the same symbols as shown above.
Next time, we'll talk about a couple ways to access all symbols in the Unicode character set, whether they've been programmed into the IME or not. Stay tuned!