On your pink ballot paper there's a list of candidate's names and then two columns for you to mark your first and, if you wish, your second choice for mayor of London.
The mayoral election uses the supplementary vote system, which gives you another chance if your preferred candidate doesn't come in the top two slots.
If one person gets more than half of all first-choice votes they win straight away.
If not, everyone except the top two candidates is eliminated and the other candidates' second choices are counted. Whoever has the most votes after that wins.
It is likely that fare-cutting Ken Livingstone and bankers' buddy Boris Johnson will be the final two candidates, so to make sure your vote counts at the end make sure to put a cross next to one of them in at least one of the columns.
For example, if I put the Green candidate Jenny Jones as my first preference and Ken Livingstone as my second, then if Livingstone makes it into the final two and Jones doesn't, my vote will count for Livingstone.
On your yellow ballot paper put a cross in the box next to the person you want to represent your area.
The 14 constituency elections are done by plain old first-past-the-post, just like voting for Parliament.
You get one choice and whoever gets the most votes in your area wins that seat.
As you only get to pick a single candidate you may want to consider choosing tactically and voting for a big party over a small one.
On your orange ballot paper put a single cross next to the party or individual you most want to see elected to the London assembly.
For the 11 remaining assembly seats you pick once from a list of political parties and independent candidates.
All their votes from across London are pooled and a mathematical formula, the d'Hondt method, is used to determine who gets a seat.
Anyone with less than 5 per cent of the vote is eliminated. Then the remaining votes are divided by the number of seats already won plus one.
This happens 11 times, with whoever has the largest number in each round getting a seat.
For example, say Party A wins 10 constituency seats and gets 55,000 city-wide votes and Party B wins four seats and gets 40,000 votes.
Party A's votes are divided by 11, to make 5,000, and Party B's votes are divided by five, to make 8,000. Party B would get the first London-wide seat.
In the second round Party A's 55,000 votes would still be divided by 11 but Party B's 40,000 votes would now be divided by six.
This is repeated until all the seats are given out.