Due to a lack of space at the commemorative site, authorities will hold up to 1200 pilgrims at a separate location along the beach until an hour before the ceremony.
The 100th anniversary service is restricted to 10,000 ticket holders – including 8000 Australians – who secured their place through a ballot.
There’ll also be 500 official guests.
The Anzac Commemorative Site on the peninsula has 5000 seats, while another 5000 people can squeeze into a grassed area – but only if everybody is standing.
In the past, pilgrims have spread out overnight in sleeping bags or under blankets.
“So overnight when people are taking up a bit more space, because they’re lying down, we’ll be holding around 1200 people at a staging area outside the site where they’ll be able to see the reflective program on a screen,” services director Tim Evans told reporters at Anzac Cove on Tuesday.
“The last 1200 people to arrive will be held at the staging site at (Kabatepe) and brought up to join the service around 4am or 4.30am.”
As the Australians and New Zealanders on the grass are asked to stand, those who have been waiting off site will be brought in on shuttle buses. The hour-long service begins at 5.30am.
There’s more room, however, at the Australian service at Lone Pine later in morning. An additional 3000 seats will be trialled on Anzac Day this week.
The new arrangement will boost Lone Pine’s capacity to 8500 to match the number of Australians and official guests expected in 2015.
“It’s a dress rehearsal,” Mr Evans said of the 99th commemorations on Friday.
“What you see in terms of the infrastructure at the Anzac Commemorative Site and Lone Pine is the same infrastructure that will be there next year.”
New Zealand has its own commemorations later in the morning at Chunuk Bair after the joint dawn service.
Such is the interest in the 2015 centenary that six or seven cruise ships are likely to anchor off the peninsula, with passengers able to watch the dawn service via a live feed.
Mr Evans said the ships would be at least one nautical mile offshore, partly due to the risk of unexploded ordnance.
There will also be a security perimeter around any visiting warships.
Australia is considering sending a vessel or two – for the 90th anniversary in 2005 it was HMAS Anzac – as is Britain.
“The cruise ships would be out beyond that,” Mr Evans said.