Post Grad Move to Chicago

Hi All,
I am graduating in May and starting a job around July/august in the city. Hoping to move somewhere in River North. Are there any rules of thumb like when I should start looking for an apartment? Can I only lease if I am moving in soon? How does it work in Chi town?

Ive lived in New York for a summer and finding an apartment was a shitfest and renting in my college town happened like a year in advance so I'm lost.