I applied online. The process took 3 weeks. I interviewed at Chicago Park District (Chicago, IL) in May 2014
Interview
First wait for hours to take a swim test that takes ten minutes. Then if its your first summer, you have to do a week long training class. Otherwise you have to do day long testing on lifeguarding skills and cpr. Then you get an interview where you find out where you're gonna work for the summer. People get assigned to locations based on a first come first serve basis.
Good is was good, easy stuff, anyone can do it truly. Very informal no need to stress about it, simple quesitons about goals and ambitions. Why you want to be a lifeguard, no need to prepare ahead of time