The most important part of any hour-long TV show is its gimmick. Every great drama has one. The best way to think of one is to think of the world you live in and then imagine “What if?” For example, “What if a plane full of people crash-landed on an island and what if that island was magic?” This is no doubt the exact process by which JJ Abrams conceived the hit television series, Lost.
Once you have your gimmick you'll need to think of a plot to flesh your idea into something that can continue for season after season. After all, there's no reason to write yourself into a corner with an idea that can't be sustained when you could be cashing in on this idea for the next ten or more years! The news is a great place to start when looking for plot ideas. America is a big and dangerous place right now, and the people in it are terrified. Now it's up to you to take these scary and confusing stories and boil them down into forty-two minute narratives that make them simple and easy to understand. It's practically your civic responsibility!
Another thing to consider when writing the plot is this: America loves conspiracies. An overarching mystery of subterfuge and corruption can be the difference between dollar signs and a life of prestige and working for a dry cleaner's the rest of your life, wondering how it went so wrong. The higher up it goes, the better. If your conspiracy involves the government, make the person behind it the president, or one of his chief advisors; if it's the police department, make it the chief of police; and if it's a large corporation, do your best to get the CEO involved. The public will be eating out of your hand and begging for more. Just remember one thing: you are much smarter than your audience. When it comes time for the big reveals and explanations, make sure to make it as simple as possible. If you can, repeat the information more than once. And if you earlier made some sly allusion to what might happen, make sure to flashback to this scene. Chances are good your audience has already forgotten.
I bet you think you've read enough about plot, don't you? Well there's just one last thing, and it ties into your audience's tendency to forget things. As much as the public loves a good mystery they're still gonna have trouble following all the details. After all, it's been a whole week since they saw the last episode. Remind them. And whenever possible try to balance the big mystery with lots of little self-contained episodes that have nothing to do with it. Self-containment is your best friend. It simultaneously pads out your season and provides a convenient entry-point for newcomers to watch and enjoy the show, so they don't feel stupid for not knowing what's going on.
Now that you have your plot you'll have to think of the kind of people that can exist inside it. Characters are important to any show, because they provide vital human interest stories. A great way to introduce human interest is the love triangle. Take three characters, two male and one female, and throw them into situations together. If good-looking males and females spend enough time together they're bound to fall in love. Everyone knows this. Before you can snap your fingers the tension will be as thick as your bank account balance. Which one will she choose? Will she regret her choice? These stories feed directly into strong American ideals like competition and fighting to get the one you love. But remember: happy couples are boring couples. Once she's made her choice and two of them get together, give them problems. Every episode think of some new difficulty their relationship has to overcome. The public loves drama. Finally, under the weight of these insurmountable difficulties, break them up. This is great because now both characters are free to pursue other love interests, starting the romantic and dramatic tension all over again, which is the most exciting part for audiences to watch.
The last thing to know about characters is this: like people, they aren't perfect. They have flaws. Things like: works too hard, is stubborn, angers easily, cares too much are perfect because they're easy to accept and can, potentially, generate more drama. But make sure when you're creating these flaws that they aren't too flawed. After all, these are the good guys.
Now that you know everything there is to know about characters, love triangles, human interest, conspiracies and gimmicks you're ready to sit down and start achieving your goal of riches and perfect television entertainment. Good luck.