There are many different ways to prepare yourself to play a role in a film and it can feel like a daunting process. Just getting off book is a tough task on its own. But if you really want to take your acting to the next level you need to beyond basic preparation and what's present in the script and create a fully fleshed out character that you can live in during production. And the best way to do this is to research the role.
Research the character within the script
Read the script multiple times, taking notes about your character.
Try and answer the following questions (though some answers will need to be inferred)
Who, What, When, Where, Why
At the most basic level, an actor should identify:
Who the character is (in general, high-level terms)
What they want (goal)
When the story takes place
Where the story takes place
Why they want to reach their goal
After this initial breakdown is down, you can dive deeper into the character by examining their sociographic and psychographic characteristics.
Where do they live specifically and how does that affect them?
How much money do they likely have?
What is their job?
What hobbies do they have?
Who are their friends?
What class are they part of - lower class, middle class, upper class?
Are they single? Married? Kids?
What is their flaw? How does this manifest in their life?
What pain do they hold on to?
What are they most afraid of?
What are they ashamed of?
What are they proud of?
When are they the most relaxed?
What is their dream in life? Just try and imagine it.
What is holding them back? What will it take to break through?
What are their fantasies and secret desires?
Pay attention to these internal workings.
Secondly, look for surface-level characteristics that can give you a clue as to who they are.
How do they dress in each scene?
What is their vocabulary like?
Any unique words or a location-specific accent should be noted.
Conduct background research on similar real-life characters
If you want your character to come across as authentic and believable, it's a good idea to do some research into how real people with similar backgrounds to your character normally live life.
I will use the example of a character named Antonio. Let's say he is a poor third-generation fisherman from PEI who wants nothing more than to leave town and chase his dreams of being an entrepreneur in Toronto, however his traditional father has had his heart set on him taking over the fishing boat.
Where to begin? Research the fishing culture. Watch interviews, reality TV, and anything you can find on YouTube that will give you an insight into what it actually feels like to live the life of a fisherman. What motivates them to brave the wind and waves in search of a big catch? Surely this makes them unique - and this must impact how they see the world or be a result of it.
Take notes on their vocabulary and pronunciation. Familiarize yourself with the terms they are referencing. Listen to what they aren't saying too. That often reveals a lot about character.
If you live near a fishing town, maybe ask if you can job shadow someone for a day, or spend an hour with them on shore. Any time you can spend together will be valuable. You'd be surprised how much you can learn by simply chatting with someone!
What about the dreamer aspect of the character? How can you research that?
Well, ask yourself what would it feel like to be a young person with big dreams trapped in a small town? Being torn between responsibility and desire is something we can all relate to at some level.
As for researching this aspect of the character, I'd recommend touring a small town. Instead of driving through like you normally would, get out of the car, walk around a bit. Talk to the locals. Have lunch at the local diner.
Immersing yourself in your character's world will allow you to begin seeing things through their eyes. Spending a couple of weeks researching your character also will help give your acting depth and make performing in the role more enjoyable. Never forget that preparation is the mark of a true professional, regardless of the role you're playing. Research is the best way to prepare.