Braking against the interstellar medium (and possibly the stellar wind as you get closer) using magnetosail-like devices… between the stars isn’t completely empty but has a diffuse plasma that can be pushed against magnetically or electrostatically. This is how you’d slow down in pretty much any scenario as it is “propellantless.” It’s a big challenge to get the superconducting coils light enough, but it is a critical piece to interstellar flight, particularly if crewed.

Well... I like the beamed energy idea. It works to get you out of the solar system. But how do you continue to accelerate from other stars? You fire ahead of you a construction kit for a solar-powered beam-generating station. That beam station can be used either for acceleration or for braking.

But how do you get the kit to decelerate? (Remember, you fired it ahead of the ship.) And this problem gets worse as the velocity of the ship goes up. If, say, your construction kit enters a solar system at 0.1 c, it's going to cross it in maybe twenty days. I don't think that's enough time for a solar sail to effectively decelerate it. It's probably going too fast for using planets' gravity to slow it down. And using atmospheric drag is an explosively bad idea.

I don't have an answer...