Bayern, beaten last season in the final by Chelsea on a penalty shoot-out at their own Allianz Arena, are hoping to go one better this time round.
Germany international Lahm told the TZ newspaper: "The goal must be to progress as group winners.
"It will be difficult but tomorrow the fun begins against Valencia.
"They are a top team that almost always plays in the Champions League so they are just behind Real Madrid and Barcelona.
"It will be a real test and certainly they are the toughest opponents in the group."
Bayern new-boy Javi Martinez will be hoping to get his first start following his 40 million euros move from Athletic Bilbao last month.
The Spaniard has come off the bench in the Bundesliga wins against Stuttgart and Mainz but could make his Champions League bow against a team he knows well.
"I've never played in the Champions League before and it's an important match for us," he told the club's official website.
"Bayern made it to the final last season, and we're among the favourites for the competition, so we obviously want to make a successful start.
"I know their team very well and I've played them quite a few times. They'll definitely push us hard because they have a great team.
"They're very balanced, they have plenty of pace, they put opponents under pressure, and they're very well set up tactically."
Valencia striker Roberto Soldado is expecting a tough encounter in Bavaria.
"If there is a favourite, then it is them because of the level that they showed last year in the Bundesliga and in Europe," he said.
"They are a very strong team, but we are going there to do everything possible in order to take the win."
Valencia drew at Real Madrid on the opening day of the Spanish season and were narrowly beaten 1-0 at Barcelona earlier this month despite an encouraging display at the Nou Camp.
Spain international Soldado added: "The important thing is to start well, although we know that they are hard to beat at home.
"Bayern are a team who are on a par with Real Madrid and Barcelona - against whom we have already played (this season) - and we are going to try and respond in the same way in Munich."