Can you expand on what you believe is the best way to show your abilities? How do you get pass the gatekeepers? How do you make sure your getting leveled at the right level during the process?

Yes, there are actually people with real life issues who actually face this scenario.

"Gatekeepers" are usually HR, recruiters, or some sort of sourcing agency. Unfortunately resume buzzword bingo is a fundamental of that type of low quality screening. You can get high quality contacts through other methods. Open source contributions, "published" papers, public presentations, and mailing list comments all provide very good signal for recruiting candidates. Old fashioned networking through peers, user groups, and conventions can not be beat. Those types of contacts usually lead to an internal referral, which is one of the best indicators for hiring.

By "show your abilities" i was thinking of during the interview. When someone asks you how to implement a linked list (ugh) ask questions, use code comments, note edge cases and optimizations, heck write a quick test case to go with it. You can also accomplish via the open source contribution route noted above. A key point is demonstrating knowledge of a problem domain instead of asserting it.

WRT "correct" leveling its very hard to get right. Frankly you, as the candidate, will have a difficult time succeeding with an assertion of "im quite senior". Besides the aforementioned technical ability leadership is incredibly important for senior positions. Its your job to increase the value of your coworkers. A very powerful technique is conveying information through the questions you ask. Asking abiut mentoring opportunities and team growth are positive signals, for example. Ask questions if have concerns during the process. "What types of problems will i be solving" or "how will my work affect customers" might give you insight in to how youre viewed.