Interviews are beginning to choose the 70,000 'Games Maker' volunteers who will work at the London 2012 Olympics.
The first selection centre is opening at ExCel, London. Events around the country will follow, in the UK's biggest peace-time recruitment drive.
Up to 250,000 people applied to be volunteers, meaning most will not make the 100,000 shortlist to be interviewed during the next 14 months.
Their roles will include taking tickets and accompanying athletes on site.
London Organising Committee of the Olympic and Paralympic Games (Locog) chairman Lord Coe said: "I know the difference between a good games and a great games is the quality of the volunteers.
"The Games Maker volunteers will be the faces of the London 2012 Olympic and Paralympic Games and it is crucial that we recruit the best team players in the UK."
The London centre will be open from 1 February to 31 March.
The Games Maker recruitment event will then travel to eight other UK centres in the Spring and Summer until mid-August.
About 300 people a day are expected to attend and have a 30 minute interview.
Offers will be made at towards the end of 2011, with training to follow in 2012.
Olympic gold medallist Jonathan Edwards said the volunteer process was the chance to be part of the "once in a lifetime opportunity" that the Games presents.
"Being a volunteer at the games, helping to put it on, helping to make history, perhaps rubbing shoulders with some of the wonderful athletes, making the whole thing tick. Who wouldn't want to do that?" he said.
Jean Tomlin, Locog's HR director, said a variety of general and specialist roles were available and she was looking for "passionate, committed" volunteers.
She said: "The stage we're at now is matching those skills detailed in their application form with the roles we have across our venues across the UK.
"There are phenomenal opportunities to be accompanying athletes on to the field of play, working with press, broadcast, ticket takers, uniform distributors.
"Opportunities to be part of the games and deliver a great service to your country.
"We got a quarter of a million people. Unfortunately I can't take them all, I'm going to have to turn some down and select 70,000."
At ExCel, with 543 days to go until the Olympics begin, would-be volunteers said they were happy to take the roles offered, and felt it would present a "unique" opportunity.
One hopeful, Dawn Bracken, said: "I'm passionate about the Olympic Games. As soon as we won the bid I put my name forward as a volunteer.
"I've been working in the offices at 2012 for the last two years so hopefully I'll have a role at Games time."