On the editing page of every entry, there are a set of quicktags that allow you to format text.
If you play with these a little you'll come to understand what Wiki code looks like. Generally you format text by surrounding it with certain repeating symbols.
Underline: 3 "equals" signs (=) on either side of the text. ===like this===
Bold: 2 underscores (_) on either side of the text. __like this__
Italic: 2 single quotes (') on either side of the text. ''like this''
Centered: 2 colons (:) on either side of the text. ::like this::
Strike-Through: 2 hyphens (-) on either side of the text. --like this--
Words connected with a hyphen or written together, like Austro-Hungary or McCoy will automatically be recognized as wiki-links. To prevent this, use the non-parse tags:
Some of the formatting codes I find particularly useful are the title bar code, which is a minus sign (-) and an equals sign (=), then text, then the equals and minus in reverse order. It looks like this:
Here is a title bar.
-=Here is a title bar.=-
Also, the box feature is handy. You can do this by putting one carat (Shift-6) on either side of your text, like this:
I'm in a box!
The other formatting trick to know is how to work with tables in Wiki code.
A table starts with two bars. Each new line creates a new row in the table, and cells within a row are divided by a single bar. If you skip single bars in a particular row, that cell spans the remaining length of the table; if you put just a space between two single bars, the cell will be empty. The table is then closed with two more bars. So if the code looks like this:
Then you get this:
|table cell 1||table cell 2||table cell 3|
|table cell 4||table cell 5|
|table cell 6|
You can play with the other buttons, too, to see what they do. See Making A Wiki Link and Adding Images for information specific to those two formatting methods.
You find more formatting options and help with formatting problems by clicking on the help "?" at the top right corner of the edit box: