After putting on a clinic during the match, Roger Federer gave another one afterward.

Prompted in the on-court interview after his 6-3, 6-2, 6-2 U.S. Open victory over Israel's Dudi Sela on Thursday to give the tennis players in the stands a few quick pointers about how to dial in their serve, Federer offered this advice.

"It all starts with a good ball toss," he said after moving easily to the third round. "Sometime, people think it's just the swing, but I think the ball toss creates your motion after that. You should keep your elbow high on the serve, then the better you get, the more you can use rotation and legs."

It worked great against Sela. Federer finished with six aces and maxed out at 128 mph in what looked very much like a tuneup — a second-round win that took only 1 hour, 17 minutes.

Federer came into the U.S. Open as the third seed and is trying to avoid going an entire year without a major victory for the first time since 2002. He turned 30 on Aug. 8, prompting questions on how long he can play at an elite level.

Against the 93rd-ranked Sela, though, none of this was an issue. Federer improved to 58-6 for his career at the U.S. Open.

"It's tough to play him, especially when you're not at your best and on center court," Sela said. "On Court 25, maybe I'd have a bigger chance. I had no chance against his serve."

After the Federer match, No. 28 Serena Williams took the court at Arthur Ashe Stadium and had an equally easy time. She beat Michaella Krajicek 6-0, 6-1 in 49 minutes to end the day session before 4 p.m. — about three hours earlier than normal. The other day match in Ashe was No. 7 Francesca Schiavone's 6-1, 6-1 victory over Mirjana Lucic.

Williams, who pulled out of a tuneup match in Cincinnati last month, hasn't lost a match in which she's actually taken the court since the round of 16 at Wimbledon.

"I just try to keep enjoying myself and just have fun, whether I win or whether I lose," she said. "It's a great honor to be playing out here."

No. 1 Novak Djokovic and No. 8 Mardy Fish were scheduled for later matches, as was top-seeded woman Caroline Wozniacki, in search of her first major title.

In other early action, No. 16 Ana Ivanovic got a walkover when Petra Cetkovska pulled out with an injured quadriceps.

"It's never nice to win this way," said Ivanovic, a former No. 1 moving her way back up the rankings after a drop into the 60s last year. "But I'd be lying if I said I wasn't happy to be through to the next round."

No. 11 Jelena Jankovic and No. 18 Roberta Vinci also advanced in straight sets while No. 10 Andrea Petkovic needed three sets to get by Zheng Jie of China.

On the men's side, ninth-seeded Tomas Berdych defeated Fabio Fognini of Italy, 7-5, 6-0, 6-0, while No. 7 Gael Monfils took a 2-1 sets lead over Spain's Juan Carlos Ferrero.

Williams is now carrying the family banner at the Open. Sister Venus withdrew on Wednesday, citing a recently diagnosed autoimmune disease, Sjogren's syndrome, which can cause fatigue and joint pain. In an interview Thursday on ABC's "Good Morning America," she said she plans to return to tennis.

"Sjogren's is something you live with your whole life," Williams said. "The good news for me is now I know what's happening after spending years not knowing. ... I feel like I can get better and move on."

She said she suffered from swelling, numbness and 'debilitating' fatigue.

Asked after her match how she felt about her sister's withdrawal, Serena Williams said, "Venus is a great woman and super tough. I've been praying for her. She'll be fine. This is just another battle."