BRUSSELS -- The new year will see a changing of the guard in Brussels, with top posts at NATO and the major European institutions changing hands.NATO will get a new secretary-general; new presidents will be sought for the EU Commission, the European Council, and the European Parliament; and hopefuls will jostle to succeed Catherine Ashton as the EU's foreign-policy chief.Three of these posts -- European Commission president, European Council president, and EU foreign-policy chief -- are interlinked. The successful candidates should reflect a geographical, gender, and party-political balance and they should also be ready to give up their national careers back home. The NATO secretary-general is not directly part of this equation but it's unlikely that he or she will come from the same country as any of the three above.Since 2004, Jose Manuel Barroso has been at the helm of the EU's executive, the body that proposes EU rules on everything from agriculture to financial regulation and makes sure that countries later implement those laws.Barroso's second, five-year term ends on October 31, and the process of selecting a successor might provoke a real fight between the two European institutions involved in the task. They are the European Council, the gatherings of EU heads of state or government, and the European Parliament.That's because this will be the first time a commission president is selected under the Lisbon Treaty, the EU's updated rulebook, which came into force in 2009 and gives the parliament more say in the process. While the council, as usual, will nominate a candidate for approval by the European Parliament, this time EU leaders must put forward a name "taking into account" the results of the May European Parliament elections.As Sonia Piedrafita from the CEPS think tank notes, it's not really clear how this will play out. "We don't know how the council first will interpret the wording of the Lisbon Treaty, that just says [it] 'will take into account the majority in the European Parliament.' But that can be read in many different ways," she says.The political party groups in the parliament have already started putting forward their preferred choices.The Socialists want current parliament President Martin Schulz to get the commission top spot if the group emerges on top after the parliamentary elections.But Schulz has several factors going against him. German Chancellor Angela Merkel isn't a fan. Many EU member states want a current or former prime minister for the post. And he is German, which puts off those who think Berlin already wields enough power in Brussels.Another possible candidate is Danish Prime Minister Helle Thorning-Schmidt. She would be the first female commission president; comes from a small country; has previous experience as a member of the European Parliament; and looks like she could fare badly in the next Danish elections -- meaning a Brussels job might be an appealing alternative.This post was created by the Lisbon Treaty to give the European Council its first full-time president, serving up to two consecutive 2 1/2-year terms. The job is likely to go to a consensus-builder in the mold of current President Herman Van Rompuy, who was chosen by the council five years ago and who steps down on November 30.A likely candidate would be someone who doesn't take away the limelight from national leaders. "What do member states' governments want? We have seen in the past they have been tempted in the end and also took decisions not to take the potential strongest candidates, but look for candidates which are able to strike compromises, candidates which they are able to influence, especially from the key member states," says Janis Emmanouilidis from the EPC think tank.If the commission goes to a left-winger, this one will go to someone on the right. The role of this post consists of pushing the EU's 28 member states to reach consensus, so watch out for two real Brussels stalwarts: former Italian Prime Minister and European Commissioner Mario Monti and Jean-Claude Juncker, who just stepped down as prime minister of Luxembourg after 18 years in power.Another post created by the Lisbon Treaty -- the high representative of the union for foreign affairs and security policy, to give it its full title. This combined two jobs into one with the aim of giving the EU more foreign-policy clout. Catherine Ashton, who has held the job since 2009, will step down in December, and there is already a clear front-runner to succeed her: Radek Sikorski. The Polish foreign minister is reportedly learning French and it's felt that it's time one of the top posts in Brussels went to one of the newish member states in Central and Eastern Europe. Sikorski is well positioned to replace Ashton, unless his current boss, Donald Tusk, wants to go for the commission job or.......if Sikorski hasn't already got the job replacing Anders Fogh Rasmussen at the helm of NATO. Rasmussen has chaired the military organization's main decision-making bodies since 2009. The alliance should have its new head appointed just before or at the NATO summit in the United Kingdom in September. Other potential candidates include British Foreign Minister William Hague, his colleague at the Defense Ministry, Philip Hammond, and former German Defense Minister Thomas de MaiziereUsually the two biggest groups, the center-right European People's Party and center-left Socialists and Democrats, perform the "Brussels stitch-up," in which they allow their respective leaders to chair the assembly for 2 1/2 years each. This was the case, for example, when Social Democrat Martin Schulz replaced Christian Democrat Jerzy Buzek in 2012 as the chairman of the EU's only directly elected body. Since May's European elections are likely to see a large influx of euroskeptic and far-right parties -- such as the United Kingdom Independence Party, the French National Front, and Geert Wilders' Party for Freedom in the Netherlands -- the balance might be shaken and all the other parties might unite behind a compromise candidate from the smaller, but staunchly pro-EU Liberal Party.