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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.