Here's one way, certainly not the only way.
First, create an interesting character; you can just make up someone, or use a combination of people you know to create the character.
Give them a problem or conflict.
Put the character in whatever setting best shows the character dealing with or solving their problem.
A couple of examples pulled out of the air.
A drama:
Phyllis is a widow with three kids, two boys and a girl, ranging in age from 23 to 30. Phyllis is a likable person but has always been a domineering mother, to the kids' utter annoyance. Each of the kids have learned to deal with their mother in their own way; one is sullen, one fights back and argues with her mom, one keeps as far apart from mom as he can. Each of the kids have their own goals in life, maybe one wants to be an artist, one is trying to keep his struggling business afloat, one has his own family and set of problems (he and his wife are separated but they haven't told mom).
Phyllis has been put in the hospital where she learns she is dying and doesn't have long to live. True to her nature, Phyllis still wants to control each of the kids' life, almost from beyond the grave. The kids are trying to "be nice" but it's always hard with Phyllis. The play could be a scene in Phyllis's hospital room where Phyllis and the kids (and maybe Phyllis's sister or a friend or Phyllis's daughter-in-law) voice their life and desires, discuss their problems in the past, and try to come to some understanding while there's still time. The ending can be as bittersweet (and hopefully moving) as you want it to be.
A comedy:
Ralph is an ordinary working stiff, say a cab driver. Ralph's wife is both a complainer and spendthrift; she always has to have the best of everything and must "keep up with the Jones." Ralph is always over his head in debt. The wife is also the nosy type, Ralph has never been able to keep any secrets from her.
Ralph has just won the lottery, a million dollars. He knows his wife will go through the money in less than a year if she finds out about it. The play could be a series of scenes in Ralph's living room where he does everything to keep his wife from learning of the money . . . friends who know about his winning the lottery drop by to congratulate him (to his wife he pretends they're talking about something else), there is a story in the paper about Ralph (he must keep the paper from his wife at all costs); maybe as part of winning, Ralph has been given a new truck (how to explain it to his wife), maybe Ralph's wife is complaining about what little they have and it's all Ralph can do to keep from telling her about the money himself, etc,. etc. You could have Ralph be somewhat like Ray from Everybody Loves Ray (or a Tom Hanks kind of guy), while his wife is like one of the characters from Desperate Housewife. Play up the desperation and hopelessness of Ralph's situation.
Neither of those ideas may not work for you, they're just examples, but you're welcome to use them if you like. It would probably be better if you created your own characters and situations and go from there. Find something, or someone, you find interesting.
Good luck.
ac