<p>What is the best practice of Unicode processing in C++?</p>

Here is a checklist for Windows programming:
All strings enclosed in _T("my string")
strlen() etc. functions replaced with _tcslen() etc.
Use LPTSTR and LPCTSTR instead of char * and const char *
When starting new projects in Dev Studio, religiously make sure the Unicode option is selected in your project properties.
For C++ strings, use std::wstring instead of std::string