How to cast your votes

As the candidates criss-crossed London in a final bid to drum up support many voters were still uncertain how the complicated voting system works.

Voters will get three ballot papers - a pink for the Mayor, yellow for their local London Assembly constituency and peach for the London-wide Assembly list.

MAYOR: While Mr Livingstone and Mr Johnson have dominated the race, there are 10 candidates standing for London's top job, including Lib-Dem Brian Paddick and Green Sian Berry.

Londoners will be asked to pick a first and second-choice candidate and to mark each box with a cross. With the race between Labour and the Tories so close the second-choice votes, from Mr Paddick's supporters in particular, could decide who wins.

If no single candidate wins 50 per cent of the first-preference votes the top two candidates - expected to be Mr Livingstone and Mr Johnson - will go into a run-off. All other candidates will be eliminated and their second-choice votes will be added to the tallies of the top two.

The winner, who will be the one with the highest combined total, gets to serve as Mayor for a fixed four-year term and have power over issues such as transport, policing, the environment and the London Olympics.

LONDON ASSEMBLY: This has 25 members and meets at City Hall, where its job is to scrutinise the Mayor and examine issues of concern to Londoners. The Mayor is not a member of the Assembly but regularly appears in front of it to answer questions. Fourteen-of its members are elected to serve constituencies that typically stretch across two or three London boroughs, such as Enfield and Haringey or Hounslow, Kingston and Richmond.

The other 11 are chosen by their parties under a "top-up" list system of proportional representation based on each party's support across London. Voters will receive two separate ballot forms - yellow and peach - to elect their " constituency" and "list" members.

For Standard readers uncertain how to vote, local government expert Tony Travers has devised a voting guide.

Tony Travers' mayoral voting guide

Voters - who must have registered on or before 16 April - can turn up at their local polling station, open from 7am to 10pm tomorrow, with or without their polling card. Staff will check their name and address before handing out polling papers. When the polls close, all the papers are sent to one of three count centres - Olympia, Alexandra Palace and ExCel - where they are stored securely overnight. At 9am on Friday counting begins and they are electronically scanned and counted.

The returning officer for each London Assembly seat will announce the result for their constituency locally, at the count centres. The results for the Mayor and London-wide Assembly members, which are expected between 5pm and

8.30pm, are announced at City Hall. In the unlikely event there is a dead heat in the mayoral race, the GLA chief executive will flip a coin. The only way any result can be challenged is by an application-to the courts for a judicial review. After the result is declared, Mr Livingstone will remain in charge over the bank holiday weekend and, if defeated, will only hand over the keys the following Tuesday. If he is re-elected, his third term will start then.

But there remains potential for confusion. A poll for the Standard yesterday found the majority of Londoners did not fully understand the complicated system.

In the last City Hall elections in 2004, more than half a million votes were lost because voters marked the papers incorrectly. That poll was more complicated because elections were held for the European Parliament at the same time. A further change has been made this year with two ballot papers for the Assembly rather than one. As polls indicate that the result could go to the wire, voters need to ensure they mark their papers correctly.

The three main candidates for Mayor took to the streets today as thousands of supporters handed out leaflets and posters. Mr Johnson joined early morning commuters at Waterloo before hopping on a special Routemaster bus to Haringey.

Mr Livingstone had four separate campaign events, starting in east London and travelling by public transport to the north, south and west of the city. Mr Paddick, meanwhile, unveiled his "secret weapon" when it came to deciding policies - his 88-year-old mother. As he visited a Kingston care home, he revealed she often briefed him on the needs of the elderly and on life in the outer boroughs.