You have commercial insurance
Most branded drugs have a manufacturer copay card that can bring your cost down to very little, sometimes zero. These are run by the drug company itself. They are real, they are underused, and they are usually buried three clicks deep on the brand's site. Find your drug here and look under Paying for it.
You have Medicare or Medicaid
Manufacturer copay cards are not available to you. Federal law prohibits it. What you can use instead are patient assistance programs and independent charitable foundations, which are a different thing and are often missed. Look for Patient assistance on your drug's page.
You have no insurance
Patient assistance programs from the manufacturer can sometimes provide the drug free. For generics, a prescription discount card is usually the fastest path and can cut a cash price dramatically.
Your drug is a generic
There is probably no copay card, because nobody markets the drug anymore. A discount card is your best tool. Prices for the exact same pill vary wildly between pharmacies, so it is worth comparing.