For low resistance resistors, it is a good idea to use the wire to
make a Kelvin four-terminal resistor - the current through the
resistor flows through two of the leads, and you measure the voltage
drop across the 1.00 ohm length of wire through two other leads. See
page 5 of the appication note below
That depends on what you have to start with. Can you accurately
measure voltage and current? Do you have an accurately-known
resistance of some other value already? Do you have a way to control
the temperature of the resistor after you make it, so that thermal
drifts and thermal emfs won't destroy its accuracy? What materials do
you have to make it from? Just how accurate do you want it?
The people who DO know how to make very stable, accurate resistors
understand not only the theory but the art: they understand how to
process the materials so that, for example, stresses don't destroy the
Do a Google search for things like "history of resistance standards"
and you'll find some info on it. The paper at http://nvl.nist.gov/pub/nistpubs/sp958-lide/html/063-065.html about
resistance standards is pretty interesting; the NBS (now NIST)
resistance standard from about 1931 up until 1990 was a set of 1-ohm
resistors that are still in use today as transfer standards.