We have to start from the fact you are a minor character, and that you know it. By definition, that means that you are not vital to the plot, story, etc.. As others have said, you must identify the main character. Although I don’t think you can depend on having meta information like finding out who the author is nor gauging your genre.
Nonetheless, you must identify the main character! Like others have said, they will be outstanding in some way. It may be easy or obvious (and possibly how you came to find out you are the minor character) or you may have to search (you could be in their flashback, and you only knew them in elementary school) or possibly the worst case, you aren’t in the story yet. You will have to maintain vigilance because at any moment they might float in and then out of your life (You might be one of the other drivers in Office Space, for instance) Assuming you find the main character(s), your real task begins. Taking a look at common character progression across most genres, to go from minor character to something more, you have to do the following:
* Interact with the main character, the more the better, and the more important/valuable you are the better. The more frequent the interaction, and more magnitude (attention) you can pull, the better.
* Become vital – remove other competing sources of whatever you provide, or simply be “the best” at it.
This can be shown in the following examples:
<PERSON> had friends in the first Twilight book. How much air time did they get in the Fourth? <PERSON> was a minor character and/or not present in the first book (I don’t recall) but became one of the main characters by the end. These changes happened solely because of how much time they spent with the main character and how much value they added to the story.
Many stories have a quest to find some object or information. The first time this occurs, the main characters spend a lot of time scouting and scheming and hunting and whatnot. The second time, they do straight to their ‘dealer’, and only if that person cannot provide will they continue their quest. Adventure Time has a chance encounter with “Choose Goose” early on, and now he is a regular salesperson. (salesgoose?). Often baddies-turned-goodies are huge sources of information. 846
At first, anything they say is suspect and can spawn side-quests and other stories. By the second season, their capacity is reduced to tomes and fact-checkers. (Hey, when you were in Hydra, did they have this superweapon?)
But, like in the examples, you can ascend from minor character to main, typically by being incredibly useful. Perhaps it is what makes main character main in the first place, their ability to succeed. Take any team-based story, and ever main character fills a role. When they leave/die, that role is filled by either a new character, or the most qualified minor character. The frequency that you appear both determines and is determined by your usefulness and apparent value.
So, to get back to the question, attach yourself to the main character and become useful. Help them succeed as often and loudly as possible. Getting noticed by the main character is about as good as getting noticed by the author and readers, as they are your ONLY chance in the long run. The more duties and responsibilities you can absorb from other characters, the more you will be discussed, referred, and consulted. The more action you can wrest from the main characters, the more “screen time” you will be afforded.
Considerations:
You cannot be evil, unless the main characters are evil. Then you can only be less-evil than them. (Yes, I meant that). You can do bad things, sure, but they have to be able to be shuffled under the rug by “seedy past” or “baddie-turned-goodie” tropes. If you are actively bad while in the temporal presence of the main characters, you will get stuck as a baddie, and will probably not say long in that story. 846