My suggestion is that you examine your career, jemagee. You've most likely followed a path of some sort, building experience and skills along the way, with an idea in place of what you'd ideally like to be doing. When a potential employer can follow your line of thinking and your career path, you're right where you want to be in the interview. Build your resume to get you to that point.
I haven't found a 'career' that holds my interest just yet
Then what, exactly, is it that you want?
While many people actually follow a path that leads into what they want to do for the rest of their careers, it often does not live up to their expectations. Sometimes, you can turn the job into those expectations, but that takes time on the job to advance to a position in which you can do so. It would help if you can decide what that might be.
As far as inteviewing for a new position goes, Joe has covered some of the needed aspects but there are important traits you need to exhibit during a job interview that can help you get hired. It does involve selling, however, so even though it flies against your nature, it helps to make you stand out in a crowd. You are selling yourself. Primarily, do your homework. Use the Internet to research the company and find out what they are likely looking for in job candidates, then become that person. This is not that hard, but is typically ignored by many job candidates.
The longer you put off getting into the field or career of your choice and education, the harder it will be to switch. Unless you are not concerned with your current treatment and prospects in being recognized as an important cog of their system, you should be looking for that career now. Management may not realyze fully how important you are to them, or worse, do not see you as being all that important. Their perception may not match your own.
So instead of demanding a raise or discussing salaries, ask your boss to give you a job review. Tell her you are concerned about your future with the company and need to know what direction the company is going and where you fit into those plans. Be prepared to discuss particulars about your job - SELL your job to her, but not by using terms like "my flawless skills were the only thing that guaranteed success", "So and so knew nothing about it, but I saved the day for her", blah, blah, blah. That won't work. It is best to get your supervisor to tell YOU how you contributed by asking direct questions, such as "what do you think about the work I did on such and such?".
Do not expect immediate action, but listen very carefully to what she has to say. It may turn out that she has no idea how much you do and how you do it, so be sure to explain exactly how you worked on a project without talking directly of others. This is about YOU. At the end of the discussion, tell her you enjoy the work you do (be sincere regardless of how you REALLY feel), but that you are unsatisfied with the compensation. Then ask her if you can do something that could change that and what that might be.
Yes, this is selling a product - YOU, but do not dispair about that. Just be prepared before talking to her. You want the discussion to provide essentially a status update of your worth to the company and to your supervisor so the seed gets planted that you provide skills not readily available not only within the company but in any future hirings of the company.
Then start planning a career change into the field you want to BE in. This is your practice company. Look at it that way.
