Ferber method

For those of you who have done this method and succeeded... I have a few questions. I know you wait 5 minutes then 10 minutes then 15 and so on. My question is after I lay her down do I go in after 5 minutes no matter what? Or do I only go in 5 minutes if she is crying? Also, when you go in do you stay until they are calm again or just reassure them and leave? Thanks in advance!