Lets look at one of the more common ways of generating entanglement- in the example it is entangled photons...
The process we often use in the lab to generate entangled photons is called Spontaneous Parametric Down-Conversion. In SPDC a laser with frequency (essentially the color) of X is sent into a special crystal, as it passes through and interacts with the crystal some of the input photons with frequency 'X' will 'down-convert' into two lower frequency (lower energy) photons. The sum of the energies of these two photons will equal the energy of the original photon.

A small subset of these down-converted photons will consist of entangled photon pairs. The polarizations of each of the 2 photons will be perpendicular - if you measure one of them to be vertically polarized, then you know the other one of the entangled pair will be polarized horizontally.

Until you measure one of the polarizations the polarization state of the photons is in a superposition. Each photon is polarized in a superposition of the two polarizations.

If you let the 2 photons travel in opposite directions for a year, and then measure one to have vertical polarization, you know that the other photon 2 light years away must be polarized horizontally; the moment you measure one photon, the wavefunction of the pair collapses- the distance doesn't matter . It may _seem_ like the photons have communicated to each-other faster than the speed of light... but YOU have NOT sent any information faster than the speed of light. Some other grad student receiving the other photon and seeing it is horizontally polarized knows nothing about what is happening with you 2 light years away.

You do not have any way of manipulating your photon to somehow send information to the other. You simply do a measurement and the photon tells YOU how its polarized.

If you put an optic in the path of your photon that will rotate its polarization, you are NOT rotating the polarization of the other entangled photon. Additionally, the act of interacting with your particle to rotate its polarization may be enough to cause the wavefunction to collapse and destroy the entanglement.

similarly, the example of the two particles with opposite spin (first of all, 'spin' refers to the direction of the angular momentum vector, and while objects that are spinning have angular momentum, you should not think of the particles as little balls that are actually spinning... they simply have a set inherent quanta of angular momentum- yeah, it weird). For instance all electrons are 'spin 1/2' particles- fermions. The orientation of the angular momentum vector between 2 particles can be entangled so that the angular momentum vectors are different by 180 degrees. If you measure one to be spin up, then the other must be spin down. If you do something to change the direction of one particle's spin, then that may destroy the entanglement but it WON'T change the direction of the spin vector in the other.

I hope I have explained this clearly- its greatly simplified, but the bottom line is that there is no known way to use entanglement to transmit information, in fact if there WAS a way to do so, it would lead to a break down of causality, and would contradict Special Relativity.

TANSTAAFL