cut the stalk off as low as you can without damaging any leaves or aerial roots. put on a sunny window cill and administer 1 egg cup of water once a week. After a few months a new stalk will grow and flower. Mine is 18 months old, the initial flowers came off, it had re-flowered once, and is about to do so again.
If it is a phalaenopsis (one of the most common), it seems to be all about finding the right place for them - nice bright daylight but not burning direct sun. Cut off the stalk just above the lowest little sticky-out node bit, and just wait a while, if it doesn't flower for a long time, try a different place for a while.
Mine used to have several months off between flowerings, but I now seem to have found the "magic" spot (lounge windowsill...) and they barely stop at all - every time I think they have finished, I find another new bit of stem has already sprouted from the old one somewhere and has buds on already! They don't get much TLC at all, so I can't claim any credit for it!