So you have a new floor installed and you need sanding and polishing now?
And what product and what finish to use?
There is a number of options, as explained below.

If you use new hardwood most certainly your timber has been kiln dried.
Being hydroscopic material it will be affected by changes of ambient humidity.
In Sydney's summer season wood will most likely expand - taking up moisture - you will notice gaps in between boards disappearing and in winter when we are experiencing drier weather the floor tends to give up moisture and to shrink, hence the gaps appear again.

Every one wants to have the hardest possible finish. The kids will play on the floor, the dog lives with the family or the timber floor is on ground level with direct access from the street and there will be dust and grit brought inside.

If you use the hardest coating available on the market for example, two pack polyurethane, then your floor will be scratch resistant and maintenance free, but one disadvantage will be that it is inflexible.
Does this matter? 

This is due to the hard coating of the polyurethane which will bond the planks together and when the humidity drops the timber will start shrinking. Not having enough flexibility may cause a formation of large gaps between groups of 4-6 planks to compenasate for the shrinking process.

If your concerned then you should use Tung oil, a water based polyurethane or Oil modified polyurethane. They are also hard wearing but still flexible enough to allow some movement in timber, hence reducing the gap effect by allowing the floor to shrink consistently avoiding large unwanted gaps. Although in high traffic areas this finish may require additional protection (wax or polish).

 

Tung oil.
Tung Oil or "China Wood Oil" is an oil extracted from the nut of the Tung Tree, used by the Chinese for centuries to protect and beautify timber. Tung Oil may darken certain timbers, and does not produce the hardness or chemical resistance  of modern synthetic coatings. Used on floors where subdue gloss finish is desired.

Solvent based polyurethane
Hard wearing, resistant, not recommended on new timber floors due to the gap effect as explained above, and questionable health issues.

Water based polyurethane
Water-based polyurethane finishes are clear and non-yellowing, available in gloss, satin and matt finish. They have a milder odour and dry in about two to three hours. They are generally more expensive.

Oil modified polyurethane
Oil-modified polyurethane is easy to apply. It is a solvent-base polyurethane that dries in about eight hours and is a hybrid between an oil and polyurethane coating.

Natural Oils
This is our speciality. We use the Livos brand made in Germany with Ardvos, Meldos and Kunos oils. These are designed for allergy and asthma sufferers, made from natural ingredients such as orange peel oil and they provide a unique matte finish, also they are ideal for gyms, yoga centres and places where people frequently walk with bare feet as this finish is a pleasure to walk upon.