Are you considering exercising pre-ipo options that are unvested, to hold? If so, file an 83b otherwise you could be destroyed by taxes on unrealized income.

Normally though, people hold their stock options and sell them when they are with something. People are granted stock options say 100 shares at $20, they wait until they vest and are worth something like $60 and do a "same day sale". In this case they would be lent $20 per share, sell them, pay back the $20 netting $40 per share.