NEW YORK (AP) After showing off his top serve in an easy second-round victory at the U.S. Open, Roger Federer gave the crowd the some tips for how they can improve that stroke.

Five-time champion Federer won 52 of 60 points on his serve and didn't face a break point while beating 93rd-ranked Dudi Sela of Israel 6-3, 6-2, 6-2 at Flushing Meadows on Thursday. It was Federer's 225th career victory in a Grand Slam match, giving him sole possession of second place on the Open era list behind Jimmy Connors' 233.

Prompted by an on-court interviewer, Federer gave an impromptu serving lesson to fans in Arthur Ashe Stadium or watching on TV.

He noted the importance of a good ball toss and keeping one's elbow high, and likened his loose grip on his racket to ``like when you're holding a hammer.''