A rough size and a phone photo is plenty to start. You do not need plans
for a path or a driveway; for a shed or a house slab, have the drawings handy.
One licensed local concreter gets the job, and nobody else
Rough size, the site and a photo is usually enough for a first figure
Get the slab thickness, steel and finish written on the quote before you agree
What makes the first figure accurate
What it is: shed slab, driveway, path, house slab, yard pad
Roughly how big, even if it is paced out
What is there now: grass, dirt, old concrete to break out
Whether a concrete truck can drive right up to it
For a shed or house, the supplier's or engineer's drawings
Where the line covers
North of the river through Frenchville,
Norman Gardens and Parkhurst, across to The Range, and west out to Gracemere.
The full suburb list has the detail.