Key details on how Europeans will vote

On average in 2014, each MEP was backed by 240,000 actual voters, according to a Reuters calculation.

When will citizens vote?

On Thursday (23 May), the British and Dutch will cast ballots in line with national traditions, as the Dutch, for example, are by law not allowed to vote on Sunday, when people traditionally went to church. On Friday, Irish and Czech citizens will head to the voting stations, on Saturday people in Latvia, Malta, Slovakia, and the Czech Republic will vote, with everyone else casting their ballot on Sunday.

How are MEPs elected?

MEPs are elected based on national voting systems, so the methods vary from country to country. There are common standards, however, such as the system of proportional representation. Some member states, such as Germany, France, Spain and Britain, use closed lists: meaning parties have a fixed list of candidates and the number of MEPs that get elected are proportional to the vote share the party received. Candidates at the top of the lists are chosen first in these countries.

Parties usually need to pass a minimum threshold to get in, often set at five percent of the vote (to rule out miniscule fringe parties). Romania and France, for instance, have a five-percent threshold, while Greece has a three-percent hurdle for parties.

Other countries, such as the Netherlands, Nordic countries, Italy and Poland, use open lists, where voters chose a party or indicate who is their favourite candidate from that party, so they can influence who gets elected first.

There is also the "single transferable vote" system, which means voters can choose as many candidates as they like and number them by preference. This system is used in Ireland, Northern Ireland and Malta.

What about women?

Eleven EU countries impose gender quotas on candidate lists. In Belgium, France, Italy and Luxembourg the lists must feature the same number of men and women. In Croatia, Spain and Slovenia at least 40 percent must be women, 35 percent in Poland and 33 percent in Greece and Portugal. In some countries the gender-quotas are enforced with sanctions, but its not effective everywhere.

How many MEPs will sit in the new parliament?

The UK was intended to have left the EU by March 2019, and the European Parliament had already made plans on how to readjust its numbers after the 73 British MEPs left the chamber. The number of the MEPs should have gone down from 751 to 705, with 27 seats being allocated to 14 member states, and the remaining 46 seats scrapped.

But the UK asked for, and received, an extension to their Brexit date, and it is now delayed until the end of October, so the new parliament will again start with 751 on 2 July. But as soon as the UK does finally leave the EU, their MEPs will have to be evicted from the parliament.

How many MEPs are needed for a political group?

Voters choose national parties, that can then form groups in the European parliament to get funding, seats in committees, and have the ability to manage legislative files and better influence policy.

But because not all member states have, for instance, green or liberal or far-right parties, the race is a bit uneven. A group must have at least 25 members, from at least a quarter of member states, so that means 7 out of 28 countries currently. There are currently eight groups in the outgoing parliament, but that is likely to change with the liberals looking to include France's En Marche, and some reshuffling on the right is also expected.

When will the results be known?

While the Dutch and the British vote on Thursday, official results will only be out on Sunday night around 11pm. The parliament has set up a site where the results can be tracked country-by-country.

What happens after the elections?

Parties will quickly assess the results, and frantic phone calls will be made throughout Europe to negotiate setting up of party groups in the parliament, with the big centre-right and centre-left groups hoping to secure a majority.

The parliament has previously insisted that the next president of the EU commission should be the lead candidate from one of the large European political families - but national leaders want to hold onto their prerogative of choosing the new leader of the EU executive.

Party group leaders will meet on Tuesday (28 May) to hammer out a coalition, only hours before EU leaders meet to assess the election results.

Companies step in

An interesting feature in this year's election is that companies, perhaps drawing lessons from the Brexit referendum, have stepped in to campaign on behalf of voter turnout in the European elections. Germany's Volkswagen, the world's largest carmaker which makes half of its sales in Europe, has appealed in 16 languages to its 490,000 European employees to cast their vote, saying that a united Europe is in everybody's interests. "[A united Europe] has brought the continent freedom and prosperity following centuries of bloody wars and disputes," the company said in a statement.

German air carrier Lufthansa has painted its new global brand campaign "SayYesToEurope" on the fuselage of an Airbus A320. The world's number one music streaming service Spotify, from Sweden, has drawn up a playlist of top local artists from the 28 EU countries to showcase the bloc's diversity in an effort to encourage voter participation. US e-scooter company Lime is giving people free rides to polling stations on election day in 12 EU countries.