Is your current employer hiring? Are you / can you be involved in that process?
Your employer is only one company, but understanding its side of interviewing can help guide you in how to present yourself as a candidate.
Also, yeah, the best way is practice and self-reflection. And the best way to get practice is to do it, so submit resumes to jobs you aren't sure you really want rather than only your OMG I want this job. This gives you a chance to do some negotiation practice too, and maybe have some offers to play against.
Your employer is only one company, but understanding its side of interviewing can help guide you in how to present yourself as a candidate.
Also, yeah, the best way is practice and self-reflection. And the best way to get practice is to do it, so submit resumes to jobs you aren't sure you really want rather than only your OMG I want this job. This gives you a chance to do some negotiation practice too, and maybe have some offers to play against.