  The intrinsic alignment of galaxies constitutes the major astrophysical
source of systematic errors in surveys of weak gravitational lensing by the
large-scale structure. We discuss the principles, summarise the implementation,
and highlight the performance of two model-independent methods that control
intrinsic alignment signals in weak lensing data: the nulling technique which
eliminates intrinsic alignments to ensure unbiased constraints on cosmology,
and the boosting technique which extracts intrinsic alignments and hence allows
one to further study this contribution. Making only use of the characteristic
dependence on redshift of the signals, both approaches are robust, but reduce
the statistical power due to the similar redshift scaling of intrinsic
alignment and lensing signals.
