The 93-year-old died Friday at the Eisenhower Medical Center in Rancho Mirage.
The funeral service began at 2 p.m. at St. Margaret's Episcopal Church in Palm Desert where she and the nation's 38th president, her late husband, President Gerald R. Ford, worshipped. Members of the Ford family attended the ceremony.
Nancy Reagan, George W. Bush, Maria Shriver and Secretary of State Hillary Clinton were at the private service. Former President Bill Clinton was planning to attend, but he was forced to cancel plans after mechanical problems on the plane kept him from being able to depart.
Ford chose former first lady Rosalynn Carter, journalist Cokie Roberts and one of her sons to deliver eulogies at the funeral service, as well as Geoffrey Mason, a former director of the Betty Ford Center for substance abuse and alcohol treatment.
Ford left specific instructions to focus on friendships, a less partisan Washington of years gone by and her passion for helping people overcome substance and alcohol abuse.
"She was the tallest advocate for those struggling," Carter said. "It was a privilege to work with her about those issues."
"Thank you God for bringing us this extraordinary lady, this brave and inspirational pioneer into our lives, even those who haven't experienced the treatment," Mason said. "We're better for knowing you, Betty."
After the funeral, members of the public were invited to file past the casket and sign a guest book until midnight. About 800 people showed up.
The Fords were a longtime resident in the Coachella Valley and many people in the area remember the impact she had on countless lives.
"She was popular because she didn't hold anything back. It was no holds barred. This is me, this is who you get. Take it or leave it," said Bill Cook of Desert Hot Springs.
Jesse Pender, who was the Fords' cook for a time, flew in from Spokane, Wash., to pay his respects and share some memories.
"His favorite dish was corn beef and cabbage. Mrs. Ford was a meat and potatoes person," he said.
Ford was known for a lot of things as the former first lady, but perhaps most for her openness in dealing with her fight against breast cancer and addiction to prescription drugs and alcohol. In 1982, she founded the Betty Ford Center, a treatment and rehabilitation center to help those dealing with addiction.
Ford was also a breast cancer survivor. She underwent a mastectomy, and fans of the former first lady said it was her honesty that provided them a model of how to deal with illness.
"An inspiration to many women who had suffered with breast cancer and many people who suffered with substance abuse," said Cheryl Klabacha of Palm Springs.
The public will be allowed to attend from 5 p.m. through midnight. Those wishing to attend will be able to park their cars at Indian Wells Tennis Garden and be shuttled to the church for free beginning at 4 p.m. Officials recommend arriving at the tennis garden before 3 p.m. No large bags, backpacks or strollers will be allowed.
The four Ford children planned to attend both this ceremony and another in Grand Rapids, Mich. on Thursday.
On Wednesday, her body will be flown to Grand Rapids where her husband is interred at the Gerald Ford Presidential Museum. At another church service Thursday, Lynne Cheney, wife of former Vice President Dick Cheney, and historian Richard Norton Smith will eulogize her.
Later Thursday, her body will be interred at the museum on the day that would have been Gerald Ford's 98th birthday.
The Associated Press contributed to this report.