i recently took out my first b/b cartridge.at first it would only move about an eigth of a turn then lock up.so i went to the other side and again it would move an eighth and the stop.after much application of wd40 it started to move nice and smoothly but again kept locking.after more lubing and a lot of swearing it eventually gave up and the plastic lockring came out,then the cartridge.
what did i do wrong and should you really have two splined sockets and turn them in opposing directions(actually prob the same direction?no?)to get it out quickly and simply???

Just take the non drive side out first, so the plastic bit.

im sure thats what i tried tho and both parts turned in together

If they're corroded in badly they're a real pain in the backside.

Probably just the driveside not in tight enough and the cups corroded together, you should run a dab of greese round the BB cartridge shell where the NDS cup slips on installing the new one, should stop them sticking and make sure both cups are snugged up tight when you refit. I use a bit of coppaslip on the frame threads to stop them corroding in.