  We study the temperature crossovers seen in the magnetic and transport
properties of cuprates using a nearly antiferromagnetic Fermi liquid model
(NAFLM). For the overdoped cuprates, we find, in agreement with earlier work,
mean-field $z=2$ behavior of the magnetic variables associated with the fact
that the damping rate of their spin fluctuations is essentially independent of
temperature, while the resistivity exhibits a crossover from Fermi liquid
behavior at low temperature to linear-in-T above a certain temperature $T_0$,
due to the proximity of the quasiparticle Fermi surface to the magnetic
Brillouin zone boundary. For the underdoped cuprates we argue that the sequence
of crossovers identified by Barzykin and Pines in the low frequency magnetic
behavior (from mean field $z=2$ at high temperatures, $T>T_{cr}$, to
non-universal $z=1$ scaling behavior at intermediate $T$, $T_*<T<T_{cr}$, to
pseudogap behavior below $T_*$) reflects the development in the electronic
structure of a precursor to a spin-density-wave state. This development begins
at $T_{cr}$ with a thermal evolution of the quasiparticle spectral weight which
brings about temperature dependent spin-damping and ends at $T_*$ where the
Fermi surface has lost pieces near corners of the magnetic Brillouin zone. For
$T_*<T<T_{cr}$ the resistivity is linear in $T$ because this change in spectral
weight does not affect the resistivity significantly; below $T_*$ vertex
corrections act to bring about the measured downturn in $(\rho(T)-\rho(0))/T$
and approximately quadratic in $T$ resistivity for $T\ll T_*$.
