  The clustering properties of objects in 3 different radio surveys (NVSS,
FIRST and BOOTES-WSRT) and 2 near-infrared surveys (the ``Daddi field'' and the
FIRES survey) are investigated and compared with studies of various samples of
galaxies, AGN and clusters. At z ~ 1, it seems that the 2dF optical quasars
have a correlation length a factor of about 2 less than powerful radio galaxies
at similar redshifts. This indicates that these two classes of object can not
be ``unified'' by postulating that their main difference is due to their
evolution being at a different stage. It seems much more likely that these QSOs
are predominantly located in field galaxies, while the powerful radio sources
are located preferentially in early types. Furthermore, it appears that both
the extremely red objects (EROs) from the IR surveys and the more luminous
radio sources are similarly clustered and as such are the most clustered
objects known in the z>1 Universe. Even at z ~3 the red J-K galaxies from the
FIRES survey are similarly strongly clustered, at a level of about 3 times
higher than Lyman break galaxies. These clustering properties are consistent
with EROs and radio galaxies being similar objects at different stages of their
evolution. Locally, the most clustered population of objects are clusters of
galaxies. Since the progenitors of these objects -- proto-clusters -- will
therefore also be highly clustered, a good way to locate proto-clusters is to
target fields with very powerful and potentially highly clustered distant z>2
radio sources. The techniques that are currently being used for locating and
studying these proto-clusters are briefly discussed.
