The first thing you should know: take your GRE about 1 ½ to 2 months before your earliest important deadline. It is going to take approximately that much time for your score reports to reach the universities you have chosen as score recipients (i.e. the universities you chose to send your score reports to). Here’s what the ETS says:
The ETS sends your score to four universities free. But, if you want to sent Additional GRE Score Reports (ASRs) to more universities, you have to order them by mail or by phone. Here’s how.