Fourstring and I are looking to upgrade our windows and doors, since they appear to be the originals from when the house was built in '57. They mostly work, but are single-pane with storms and screens. We know we want double pane (duh) and tilt in for cleaning. We want high-quality, since we're planning to live here until they bring us out in pine boxes.

Info about the house - It's one-story ranch with 10 double hung (of two different sizes), one massive picture window and a small kitchen window with cranks. We are also looking to replace the front and back doors. We're assuming there will be a lot of rot in the wood around the windows, so that will be a thing.

What sorts of things should we be looking for and asking about as we call contractors?

go with the best you can afford. pocket replacements are cheaper and easier depending on the condition of your old frames? I like the Anderson windows I have but now wish I would have went for the next model up. I think Pella makes decent stuff too. windows are definitely a "get what you pay for" item.

talk to a reputable installer and get their opinion on your situation.

After replacing windows in 3 different houses , I can say , buy the good ones, get a top notch installer. Cheap ones go to crap faster than you would think( I went that way and replaced them again in one house) Also the better windows have the benefit of a noise rating, I went for the best on that and it made a huge difference. I went Colton, Anderson is also good. Spend at the upper end if you intend to stay at this house.
Remember you buy cheap , you get cheap and all its not so great problems

Our Anderson casements were original to the new house build in 1991.  They're still going strong with a couple/three seal repairs and a couple crank mechanisms replaced.  Key is, I can STILL get parts nearly 30 years later and they swap right in.  I've seen neighbors here have windows replaced twice in that same time because they went price vs quality.  Skip the junk/novelty type stuff and pay the piper. 

After replacing windows in 3 different houses , I can say , buy the good ones, get a top notch installer. Cheap ones go to crap faster than you would think( I went that way and replaced them again in one house) Also the better windows have the benefit of a noise rating, I went for the best on that and it made a huge difference. I went Colton, Anderson is also good. Spend at the upper end if you intend to stay at this house.
Remember you buy cheap , you get cheap and all its not so great problems

Good windows are expensive.  We've been working on replacing all of ours, but also are paying cash.  We've been working our way around the house and are about halfway, with the more expensive half to go.

As others have said- a quality craftsman and QUALITY WINDOWS. I have a few friends that are in the construction industry, and they all recommended Andersen, so that's what we've been doing.

My prior house had Anderson double-hung, double pane, windows with the tilt-in for cleaning feature.  They worked well.  Sometimes the tilt-in had to be cajoled a bit, but it was never difficult.  They did a good job in North Dakota, so I'm certain that they'd do great in Chicago's comparatively mild winters.