Though every recession is unique, all recessions manifest in similar ways in the real economy. By real economy, I mean the on-the-ground economy we observe with our own eyes, as opposed to the abstract statistical model reflected in official declarations of when recessions begin and end.
One characteristic that never makes it into the abstract statistical representation of recession is the light switch phenomenon: business suddenly dries up, as if someone turned a light switch off. This is especially visible in discretionary purchases, which include everything from smart phones to vehicles to eating out.
Other telltale signs of recession include:
Dead giveaway #1: businesses that seemed established and doing well suddenly close. The customers are surprised, the employees are not; they knew sales were eroding while costs were rising, and the financial situation was becoming increasingly precarious.
Dead giveaway #2: new businesses that would have thrived a few years ago close within a few months. Maybe it was the multitude of competitors, or the high rents; but for whatever combination of factors one attributes the demise to, an enterprise that seemed to have all the ingredients for success fails quickly.
Dead giveaway #3: advertising and marketing / promotion no longer move the needle. Campaigns that reliably increased sales no longer work.