Your actual achievements
You'll find several things which are very valid marketing tools in your personal experience. These are real value-adders. They'll stand out in your memory because they involved very definite results, quantifiable things where you did achieve something well above and beyond the average.
Achievements are those things which are obviously useful and productive.
You'll probably find you have more choices than you need, if you've been in your profession for a while, so pick the clearly high value events. The interviewers also need to be able to see the value, either as monetary or efficiency related, so just make that clear.
This is in many ways a much better approach for truly competent interviewees. Unlike the hard sell, these straightforward bits of information are qualified, verifiable, professional statements of fact. There's no bragging or acting involved, and you can give very good quality information.
Your personal skill sets
Long suffering interviewees will be surprised to learn that interviewers are interested in your skill sets. Again, this is an often understated part of interviews, where your job which you do so well somehow becomes nothing special, and your skills in some areas are taken for granted.
So people just don't mention that they're very good, and efficient, at their work. It's as if everyone must be great at their work, so it's not worth mentioning.
That's pretty bizarre. As anyone who's ever set foot in a workplace knows, good and efficient isn't always something you can take for granted. It's reasonable to say that most living human beings have worked with people who were never good at their work. Nor was there was ever any suggestion those were efficient, or anything like it.
If you can show that your skill sets add up to a truly useful employee, what's the problem? What employer is going to object to that? Say so, in so many words, that you really do have a good track record, and can prove it.
That topic will come up at some point in your interview, and you can keep your statement in context with any questions about problem solving, achievements, or teamwork. You may even be able to give examples in each case. Make sure you do that.
Competence is always relevant, in any interview question.
Your skill sets are major assets, and the more the interviewers see of them, the better your chances of getting the job.
Your unique talents
Going beyond basic skill sets, you now need to show abilities which are yours and yours alone.
The most basic skill you have is being yourself.
No two people are alike.
Everyone has distinct characteristics and talents.
The marketing issue here is how to emphasize those unique aspects are to the interviewers.
If you have a specific unusual ability, like mediation, or sales, you can easily include cases of your use of your skills. As marketing, it's easy. The interviewers won't need much more than a good example.
For some professions, though, the skills and talents are more subtle, and can only really be appreciated by people in the same profession. If you're a scientist or an IT worker, or for that matter a social worker or a plumber, in these cases you can get technical, and make your points as a professional. Your talents are understood properly.
Again, you'll find plenty of opportunities to show your talents in the interview. The relevance to questions is built in, just find the opportunities as they arise.
This might sound a little strange to those who've plodded through interviews which seemed very much the same.
That's because you didn't see those interviews as an opportunity for self expression, or anything beyond the average recitals of your work experience.
Marketing is different.
It's almost a completely diametric opposite to ritualized interviews with ritualized responses.
(Which, incidentally, is one of the reasons that so many dud interviewees get jobs they can't do. The interview process itself doesn't work properly. Any possibility of getting actual information is usually lost in the process of mindlessly going through the motions.)
Marketing is about information. You have far more input, and the interviewers get much more useful info to work with.