The very truth of the matter is that 99.9% of the screenplays that sell are sold based on a relationship. How you develop that relationship is a vital piece of the puzzle.
If, for instance, you're Adam Sandler's best friend, and he thinks you're funny, you could probably get a script optioned even if it's not really the greatest script ever.
However, for most people, they don't have an immediate in like that.
So for them (us, really) you have to build a relationship a different way: with a script. [Redacted--JDM] says (and I believe him) that if you have an amazing script, then people will want it, and they'll want you, and they'll go out of their way to get to you.
So that's your first step. Write the kind of script that would make story analysts weep, that would amaze audiences, that would make any director proud and honored to have shot.
Next, get it in the hands of anyone who matters. Anyone. Because, really, once it's in one person's hands who matter, it'll find its way to the one person who really matters: the one who's going to buy it.
How do you do that? Your very best options are just the top echelon of contests (almost all the others are egostrokes only), or querying topline agencies.
There will be the constant stream of people who tell you that this isn't the only way in, and they're right. I mean, how else to account for the other .1%?