- "Ashes to ashes! Junk to junk!" -Wreck-Gar
You can learn a lot about a society from how they treat their dead.
The Autobot honoured dead are placed in massive mausoleum spacecraft which are left to drift in space. These spacecraft feature a docking bay, presumably to allow Autobot pilgrims to pay their respects to past heroes. It is unknown if these mausoleums have defences to protect the dead against disrespectful Decepticons. 
A facsimile Optimus Prime was once buried when the Earth-bound Autobots believed it to be the real Optimus. This was a departure from Cybertronian traditions, but according to the Autobots present, adhering to Earth traditions was 'what he would have wanted'. When he died for real (temporarily) a short time later, his body was instead shot into space, suggesting that maybe he wouldn't have wanted a burial after all.
The Autobots have been known to dispose of a fallen enemy by giving them to the Junkions.
When Ultra Magnus was shot dead by Sixshot, he was given a burial at sea in a glass coffin decorated with Christian imagery, on his favorite planet, Earth.
The Decepticons create markers bearing the likeness of their dead, lit by an eternal flame. Superstitious Decepticons believe a deceased Transformer's spirit may linger near its marker, and it is bad luck to disturb one.
It is unclear if these mark the place where a Transformer's remains are stored or not, but at least three Transformers have markers in two locations.
For Maximals it is customary to hold a wake where their friends and comrades reminisce about their memories of the fallen.
The Predacons recycle their dead with honors. It is considered to be an act of great respect to the dead, though Maximals might disagree. When Dinobot sacrificed his life to save humanity's future, the Maximals recycled his body in honour of his Predacon heritage.
An Autobot crew who performs a noble duty and dies in battle is given a proper funeral service. The one who knew the fallen comrade the most gives the eulogy, respectful or not.
The remains of the great hero Omega Supreme, who died saving the planet, were recycled into a spacecraft. When revived, Omega seemed confused to find this had been done, suggesting that this had not been a normal practice before he died.
A great Decepticon leader, such as Megatron is given a proper funeral service. It is not uncommon for one person to erect a statue in the honor of the fallen in particular.
The remains of executed traitors are unceremoniously thrown into nearby rivers or garbage piles to rust where they lie.