Are there standard ways and guidelines on extending Unicode with custom user-defined character sets?

In a linguistic project of mine I need to use symbols not contained in Unicode. I can draw the font, but would like to avoid overwriting characters defined by the standard. Are there any standard solutions for such cases? As reserved ranges etc. I'd 开发者_StackOverflow中文版need common Unicode-aware software to handle it seamlessly.

Start at the Wikipedia article on private use characters - there are indeed specific areas allocated for such purposes (Planes 15 and 16); maybe check ConScript Unicode Registry.