The German seventh seed has reached her maiden grand slam decider, with the dominant Williams awaiting her in the final in Melbourne on Sunday.
Kerber has lost five of her six meetings with the American world number one, with her only win coming in Cincinnati in 2012.
But the left-hander is desperate to attack Williams, who hit 18 first-set winners in a scintillating victory over Agnieszka Radwanska in the semi-finals.
"Against Serena you never know how she's serving. She's serving unbelievably good," Kerber said on Friday.
"She's returning good. I think the first few balls, they are really decisive in the match.
"I must be there from the first point and playing very deep. When I'm too short, she's just going to go for it. She is making winner, winner and winner.
"I saw it yesterday against [Radwanska]. I must be ready to play my game and also be aggressive like she is."
Williams and Kerber have tried to play down expectations heading into Saturday's decider, but the former goes in as favourite.
Kerber said there was more pressure on Williams, who could join Steffi Graf in second on the all-time grand slams winners list with 22 titles.
"Nothing to lose means I can go out there and try to play like I'm playing, without pressure, without nothing," she said.
"I think when you ask a lot of people, I think most will say, 'OK, Serena will win'. But this is the challenge I can take.
"I go out there, I don't have anything to lose. I don't have so much pressure like she has. This is what I mean that I have nothing to lose.
"I know I can lose the match. That's why I'm going out there to try to win the match."