In the northeast the motto is open memorial day close labor day. Although many keep it open longer (it is going to 90 today!). We have cuctomers that only close when it starts to snow.
Closing the pool is different for different people depending upon the type of pool you have and the type of cover even. Howerver the main idea is to put chemicals in it to keep it somewhat clean over the winter, make sure undergreound lines are filled with antifreeze, bring in the filtration systems and then properly put on a cover to keep leaves and things out.
This winter I would recomend a 2nd treatment of chemicals in maybe feb, with the weather we have had it cant hurt.