"We'll have to attack, but with common sense," Guardiola, who led the Catalan club to the 2009 title in his first season in charge, told a news conference at Barca's Nou Camp stadium.
"We have to dominate and we have to be prepared, because it will be terribly hard, from the footballing point of view and emotionally too," he added.
"We have to move the ball quickly, make it fly. I know that the 100,000 fans at the ground will help us."
Last week's game was marred by ugly scenes between players and coaching staff and the arch-rivals filed complaints about each other with UEFA that European football's governing body dismissed earlier on Monday.
UEFA has brought charges against both teams and they face a disciplinary hearing on Friday.
Guardiola said he was looking forward to moving on after four games against Real in three competitions in 18 days and said he had been trying to put the off-ball incidents out of his mind. They drew 1-1 in La Liga last month before Real beat Barca 1-0 in the King's Cup final in Valencia.
"We are lucky that tomorrow everything finishes," he said. "I try to forget it. Try to focus on what we did in the first game and what mistakes we made.
"We try to prepare the second game and just focus on the match that's all."
It would be wrong to write off Real and coach Jose Mourinho, who eliminated Barca at the same stage of last year's competition when in charge at Inter Milan, Guardiola added.
"Eleven extraordinary players are going to come out, guided by a very competitive manager who wants to knock us out. The most important thing in their lives right now is this game," he said.
English Premier League leaders Manchester United will defend a 2-0 lead over Schalke 04 when they host the Bundesliga side in the other semi on Wednesday. The final is at London's Wembley stadium on May 28.
