Greece is planning to employ translators and print leaflets in Arabic to persuade at least 5,700 migrants crowding waiting areas in Athens' Piraeus port to move to regulated camps, Radio Athina 984 reported.
Migrants are currently sleeping in waiting halls normally used by ferry passengers and in more than 1,000 camping tents put up in the docks.
Meanwhile, the authorities began planning another camp for 6,300 people at a military compound near the capital in a bid to ease the pressure on Piraeus.
Overall, Greece intends to expand the sheltering capacity by another 30,000 places in the coming weeks, as a so-called readmission mechanism the European Union agreed with Turkey is due to gain momentum.
Under a deal struck by the EU and Ankara this month, any migrants who reach the Greek islands from Turkey as of March 20 who do not apply for asylum or fail to qualify will be returned to Turkey.
In practice, this is to apply to the vast majority of arrivals, up to a maximum of 72,000 people.
But many are reluctant to leave behind Europe and their chances of applying for asylum there.
"Kill us here, but don't send us back to Turkey," read a message on a banner waved by migrants in Moria on the island of Lesbos.
The practical details for the return of migrants and asylum seekers to Turkey are still being fleshed out, an EU source said Wednesday on condition of anonymity. All the involved parties are due to meet in the region on Friday to discuss the operation.
The current idea is to initially send people by ship from Greek islands to the mainland and then transfer them by bus to Turkey, the source said.
Meanwhile, the first Syrian refugees to be resettled out of Turkey are likely to be taken in by France, Germany and the Netherlands, the source added.
By midday Tuesday, 19 EU member states had pledged an overall 492 police officers and 47 experts to help the bloc's border agency Frontex with the return of people from Greece, a spokeswoman for the commission said.
The European Asylum Support Office had also received offers from 16 member states to supply 396 experts and 22 interpreters, she added, noting that 170 people were in the process of being deployed to the region.
In parallel with the return of migrants and asylum seekers to Turkey, the EU is due to start taking in Syrian refugees directly from Turkey on Monday.
Ahead of the new measures, Greece has prepared a draft law on the recognition of Turkey as a safe country to return people to.
Presently, more than 50,000 migrants are stranded in Greece, between Turkey and closed borders to the north.
However, the rate of arrivals to Greece has ebbed in recent months, while Italian Foreign Minister Paolo Gentiloni has noted a surge in North African migrants, as new paths to Europe open up in the wake of the deal and recent border closures.
Flavio Di Giacomo, a spokesman in Rome for the International Organization for Migration, told dpa that sea migrant arrivals to Italy in the year to date were roughly 18,350, about 8,000 more than in the same period of 2015.
Bottlenecks began emerging in Greece when countries along the so-called Balkan route to richer countries further north began unilaterally closing their borders.
The final stop on the once well-trodden route is Austria, whose government announced Wednesday plans to handle asylum requests even more restrictively, following the introduction of a controversial cap on arrivals.
The news came after legal experts, commissioned by the government, said that this year's planned limit of 37,500 refugees runs counter to international law. They did however add that Austria had the right to stem the inflow by other means.
Under the new restrictions, no one will be admitted unless they already have family in Austria, or unless they would face inhumane treatment or death in the neighbouring countries they would be returned to, an Interior Ministry official explained.