And the advice paid dividends.
The top seed battled past Garbine Muguruza 2-6 6-3 6-2 to move into the Australian Open quarter-finals.
Muguruza, the 24th seed, was halfway to repeating her upset over Williams at the French Open in 2014, before the Spaniard's resistance eventually weakened late.
A fan called out to the 18-time major winner to use more spin, and Williams said she made the most of the free advice.
"I did. I was like, you're right. I'm trying to do that anyway, but I wasn't doing it," the five-time champion said.
"So my fan coach was like, 'Use some spin, Serena'. I was like, 'OK, OK'.
"It's been like really great [the support].
"I hear my name throughout the whole stadium like 360 [degrees]. I don't get that everywhere. It feels good."
Muguruza conceded she failed to match Williams' steely mental resolve, after threatening to beat her for a second time at grand slam level.
"The hardest part, I mean, mentally she's amazing. She's world number one," Muguruza said.
"She has the power to be [competing] all the match without saying anything, concentrate, waiting for her opportunity.
"I mean, the serve, when she serves good, it's really difficult to return.
"And then in the back[hand], she's very strong. So it's very difficult to find the spot to beat her."
The last time Muguruza walked off Rod Laver Arena she was a loser also - to Agnieszka Radwanska - but she said her loss to Williams gave her more to build on.
"I'm learning a lot of things," the Spaniard said.
"Last year I went out of the court feeling I could do more than what I did in court.
"You know this [bad] feeling you have, I could have maybe have won a set.
"But today I gave everything I had. I lost, but I'm happy.
"When you got off the court tired, but what can I say, she played better than me.
"I have to be happy. I did fourth round. I lost to the world number one. That's it."