Williams took questions for 10 minutes a day before the world's top-ranked women's player is to compete in her first match.
She never thought she would return to the two-week tournament in the Southern California desert. She even stayed in Los Angeles an extra day because she wasn't yet ready to start the journey.
"I was a little nervous to come out here," she said. "In the beginning, I was like, 'What was I thinking?' I kind of had to overcome that hurdle."
Earlier in the day, Williams practiced with security on hand to keep fans and media away. She has played just one Fed Cup match since winning the Australian Open in January.
Last month, Williams announced her change of heart toward the tournament in a column for Time.com.
She said Thursday she was nervous informing her parents about her decision. She said they were both supportive, with her father Richard telling her "it would be a big mistake if I didn't go back. I thought that was really admirable."
Now 33, Williams is deep into a career that boasts a gaudy resume: 19 Grand Slam singles titles, the world's No. 1 ranking, and millions of dollars in prize money and endorsements earned.
In 2001, she was just 19 and matches between Serena and older sister Venus were still a novelty. Fans were tantalized by the prospect of two siblings dueling in a semifinal.
When Venus pulled out of the match 20 minutes before the start with tendinitis, boos rained down on stadium court, startling Serena. She was offended by later accusations that the sisters' matches were fixed by Richard.
"I think everyone knows that's not necessarily a true statement. But I guess you do have to ask those questions," Williams said. "I have had nothing but integrity for my whole career."
Serena went on to win the final against Kim Clijsters. Her father later said he heard racial slurs in the crowd.
"He's been through some things when he was growing up as a young man," she said. "It was a really emotional time for me when I was talking to him (about returning)."
Williams recalled praying during the final, when she fell behind in the first set.
"I said, 'I don't want to win this match. I just want to get through this moment,'" she said.
Williams learned to play tennis about two hours and a world away in Compton, California, a crime-riddled suburb of Los Angeles. She won her first pro match at the Indian Wells tournament, playing doubles with Venus in 1997. Her victory over Steffi Graf in the 1999 singles final was her first big title.
Williams has said her decision to return was influenced partly by a film about Nelson Mandela and his dedication to reconciliation.
"In order to forgive you have to be able to really let go of everything," she said. "I went through something that wasn't the best for me. Trying to get over those nerves of coming back and how will I feel and what's it going to be like. I have to experience that. When you do forgive and you do try to let go, you have to let a lot of those emotions go as well."
Venus Williams has chosen not to play in the tournament, but Serena said her sister encouraged her to come back.
Williams' return was welcomed by several other players, including top-ranked men's player Novak Djokovic.
"Sooner or later she needed to come back, so good for her that she managed to overcome the mental challenges and maybe some fear," he said.
Fifth-ranked Caroline Wozniacki described her close friend Serena as a "very forgiving person."
"She has her principles and she stands by what she believes in," she said.
Williams will play Monica Niculescu of Romania in a second-round match Friday night.