As a default, left align text. Centered text can damage readability, especially when used with lines of text. Center alignment should only be used for short text snippets or single lines, but even then, it may damage legibility by changing the start location of certain information. Magic the Gathering, Yu-Gi-Oh, and Pokemon cards use only left aligned text.
Max Line Length
Lines of text should reach a maximum of 75 characters, and more comfortably only 60. Above 75 scanning to a new line may be difficult. If a page is wider than 75 characters, it can be split into columns or given generous margins. You may use The Standard Line to adjust line length.
Minimum Font Size
Fonts should be kept above 8pt at least, and 9pt if possible. Magic the Gathering uses 9pt font, but will drop to 7.5 if absolutely necessary.
Icons to be used in text should be turned into an icon font—a font file with the icons baked in like letters. This will allow you to copy and paste the icons freely, along with ensuring that the icons always line up with the text properly. The icons should be made larger than a lower case letter.
Icons should be exceedingly simple, beyond what you may expect is necessary. As a rule of thumb, when compared with a letter, icons should be simpler, larger, and have thicker features.