I don't hang out in the community much, so I end up making my own terms. "Nether Hub" is probably correct for the rest of the community. ^^;
Anyways, the X and Z coordinates in the Nether correspond to the coordinates in the Overworld at a ratio of 1:8. This means that for every 1 block you travel in the Nether, you travel 8 blocks in the Overworld. Y distances are the same in each, I believe. Nether Portals, while seemingly chaotic, DO have an algorithm they use to locate the portal you're transporting to and, thus, can be synchronized.
The easiest way to do this, I've found, is to build a portal in the Overworld, get the coordinates, divide the X and Z by 8 (round down), and then go to the location of the resulting coordinates (don't forget the Y coordinate!) in the Nether and build a portal there. The result is that the two portals should always transport to each other.
BONUS: the direction you enter a portal is preserved between the Overworld and the Nether, so if you align your portals correctly, you'll end up facing the right direction whenever you transport.