You need to understand the proper usage of 'dees, dem, and dose'.
Seriously, it's the same as buying any other property. Place an offer. Wait for a response.
Some things to keep in mind, in Chicago, and probably anywhere. Every bank has different policies. Some will counter within 24 hours. Others might take a week or more.
The agents generally representing the banks are swamped, and not very responsive. The bank will make you feel like a prisoner and sign and sign and sign. But...you'll get a deal.
As for the actual offer, you'll want to show something strong. Banks are pricing these properties below market so coming in way under is a waste of time. The more money you can show down and the quicker you can close will help you win out in a multiple offer situation, which is common in hot areas with low prices.
And make sure you never put ketchup on your hot dog or the bank will invoke Chicago Municipal Ordinance 10.14.190.8 and confiscate your home immediately.