Russflex, hope this helps...
Best way to sell a script? Got to be great!
What is a great script? One man's art is another man's trash, (I have read a lot of trash out there and/or seen some trashy scripts make it to the screen -- haven't we all been there?). Someone, somewhere thought it would make money.
Personally, (my cheap words of advice) first, give out only polished scripts -- write and rewrite, rewrite and polish. Some readers may like. Some not so much. Then start all over again. Sounds like work? It is (still rewriting DEATH WALKS BEHIND YOU).
So take the perspective of "was it fun to write"? Please note, that if it is fun for you to write, it will show. Maybe.
My example. I give my work to others to read. Mixed results. 90% of those readers do NOT know me, (I network as much as possible these days). So little to no bias. In the past, as an example -- some readers did not like the lack of 'and' or some specific style of polished presentation (so I rewrite with 'and' while changing the questionable 'style' -- do not be stubborn beyond wise)... most important for me as a 'writer' -- did they like the story? The characters? The plot points? The distinct 3 acts? Dialogue? Arcs? Etc.?
Key questions are -- Would the reader pay to see this movie? Is it a specific actor's vehicle? Who should play X part? Who could bank roll it?
To date, no one has been smart (or insane) enough to want to greenlight one of my scripts, (I have no rich friends or family, no foot in anyone's door). So I keep writing (as I have since 1970 -- it is FUN for me to write). As long as there are those that want to read my attempts at scriptwriting, I will keep putting out (after copyrighting) scripts for others to read. Maybe, before I die of old age, one will get bankrolled. Maybe an avalanche will ensue and I can die with a smile on my face, "that I wasn't a total waste of blood and flesh".
So. Bottom line.
Is it fun to write for you? If it is not, maybe you should do something else? If it is fun, keep writing. There are worse things you can do with your life.
IF. You think OF writing just as an easy route to big money and major name making success any time your pencil hits paper or finger touches keyboard... (if you are right -- shoot me, because I am NOT rich or famous).
So, selling a script? Try to have fun while writing quality stories. Keep plugging away... do not quit no matter how many bad things are thrown your way. Or negative comments. Or mean spirited rumors. Hey, maybe add them to your story? (my 2 cents)