The thinks you need are a friend or guildie and ofcourse 2 lvl 80's.
The achievements i'm talking about are:
1 - Dwarfageddon
There is a post about getting the dwarfageddon achievement here already.
I only did it a bid different by using 1 bike and 1 Siege Engine.
2 - Take Out Those Turrets
To get the second achievement you need to clear the beginning of Ulduar till the Flame Leviathan.
Get on a bike and drive towards the door where the Flame Leviathan will spawn and as soon as he come through the door drive out of the combat zone ASAP.
Wait for the Flame Leviathan to get to his spot.
Get in one Demolisher both of you.
Person being shot to the Flame Leviathan's Turret first should aggro him by firing a rocket at him while staying outside the combat area.
He will come towards you no worries he will drive back when he's outside the combat area.
Now when he returns to his spot quickly shoot you passenger to the Flame Leviathan.
He will return to his spot and then again go to the Destroyer.
In the time he drives away and comes back you need to destroy one of his turrets.
The person attacking the turret will be thrown off him when he goes back towards his spot.
Wait till he's back on his spot and switch positions.
Explanation:
When you aggro him outside the combat area he will attack the vehicle attacking him.
When he goes outside the combat area he will reset and go back to his original spot.
When he does that you can launch your passenger on him and let him attack the turrets.
When he's at his spot again he will notice that someone is aggro'ing him and go to the destroyer who launched the passenger.
When resetting again and returning to his spot he will throw of the people on the turrets.
Good luck getting your easy to get Ulduar Achievements.