When designing a typeface there are a number of characters that I, as an English speaker, have never used, rarely seen and simply don't understand. These characters fall in to a number of different groups, but all cause the same problem. I don't know how to design them!
There are mathematical symbols. Not being a mathematician, there are some of these I am familiar with, some I am not. But even the symbols I am familiar with can cause me problems. How do I design a plus and minus sign? I know what shape they should be, but what about alignment? Should the minus sign have the same vertical alignment as a hyphen? It often doesn't but I don't know why. When I get to symbols I don't even understand the use of I am totally lost.
Some examples of mathematical symbols I am unsure of:
There are Non-English characters and diacritics. I don't speak any languages that use any characters other than the standard 26 letters of the English alphabet. I have no idea how diacritics are used or should look. I also have no idea about characters like ß (sharp S), þ (Thorn) or ð (Eth).
Some examples of of characters I am unsure of:
My current approach is to find a font similar in weight and proportions to the font I am designing and using that as a base to design from, but I'm worried I may be getting things wrong.
Are there any official sources that describe how symbols and characters should be designed? And more generally—How do I approach designing characters I am unfamiliar with?