Basically, if you have a piece of gear that requires a stat that it itself has on it ... say a chest piece that requires 100 dex and has +20 dex on it.
If you have 80 dex total, you can't wear the piece. All you have to do is throw on another piece of gear that gets you there ... say an Onyx Amulet with +20 All Stats ... then put on the chest piece, and then take off the neck.
The +20 dex will apply, giving you the 100 dex required for the chest piece .. and you don't have to keep the Onyx necklace on.
Hope that makes sense :-)