## How to create a new symbol?

I am often in a situation where I want to print a symbol within text which seems not to be in the standard packages. This means
I have already tried to [identify the symbol](http://tex.stackexchange.com/q/14/5645), but nothing worked.

Now there are two cases:

(1) I know the Unicode code point

(2) I don't even know that - I only know how the symbol should look like.


How can I create a `\mySpecialSymbol` command so that I can use `\mySpecialSymbol` within normal text in LaTeX?


For the answers, please provide an example. I think ⦝ (measured right angle with dot, U+299D) would be good. The command should be `\RADot`.