An artist is a man of action, whether he creates a personality, invents an expedient, or finds the issue of a complicated situation. - Joseph Conrad
The 2006 comedic screenplay Little Miss Sunshine, penned by Academy Award Winner Michael Arndt, isn't funny because it is full of funny characters. Ardnt doesn't put characters in a room and force them to make us laugh. Not at all. In fact, the entire family is a tragic mess: Grandpa is a foul-mouthed horny heroin addict, Frank is a gay intellectual with an inferiority complex and a recent survivor of a suicide attempt, Dwayne is an apathetic teen trying to evade family reality through a Nietzschean vow of silence, Richard is a self-involved father pushing his quixotic nine step system on "How to be a Winner" onto everyone - including his family, and Sheryl is a pissed-off enabling wife about a stones throw away from filing divorce papers. The only seemingly "normal" one of the bunch is Olive, the seven-year-old daughter who dreams of someday transforming herself into a child-sized Aphrodite and winning The Little Miss Sunshine Beauty Pageant.
Screenwriting thrives on conflict and turmoil!
Addiction. Suicide. Denial. Selfishness. Divorce. Idolization. These subjects don't necessarily seem like ideal themes to explore in a comedy. However, the best comedies really come from tragedies. But the funny stuff in Little Miss Sunshine is never "funny" characters trying to be funny. Quite the opposite. These are real people just trying to live their lives and get through another hard day. What's funny is the situation: a dysfunctional family takes a cross-country trip in their VW bus to get their seven-year-old daughter to the finals of a beauty pageant.
Imagine your own family stuck in a beat up old VW bus for two days and 800 miles. Then add in conflicts and obstacles: no air conditioning, news that your father's nine step system is a failure, your brother discovering he's color blind and can't pursue his dream of becoming a Air Force pilot, the horn of the VW inadvertently honking mile after mile, being pulled over by the fuzz, and even Grandpa dying of an overdose. Grandpa dies... and we laugh, because of the situation.
There are a number of situations in your screenplay. The first is in the beginning - the status quo - and illustrated through Act One of the script. The second situation begins when your main character is lock-in to the second act tension. This dramatic situation builds with rising action as internal/external conflicts and obstacles arise while the protagonist struggles to achieve the main objective. And a final situation begins with Act Three, once the protagonist has reached the objective and is propelled into yet a new situation with a new goal.
However, no situation will work if it is not plausible. We must believe (with genre variance) that the situations the characters find themselves in are not only plausible, but inevitable.