Well, we didn't. We sold accounting and distribution systems. The base software was functional, but basic and pretty much always needed customization. So, we sold a lot of "we can do that" features that we didn't already have, confident that we could, indeed, "do that". And we did.

There was, however, one rather spectacular disaster where the client bought really underpowered hardware for their needs. The vendor promised a more powerful machine "real soon now", but the one they had just wasn't cutting the mustard. They ended buying something much more capable from a different vendor, and then the lawsuits started happening about who said what where. We got dragged into that, but were exonerated.

Like anyone else in software, we were cocky developers, and we could do pretty much anything they threw at us. And I'm certainly not going to suggest we never missed a deadline, we all know better than that. But we knew our software and knew whatever it couldn't do, we could make it do satisfactorily for the client. I was both developer and pre-sale tech that helped keep the sales guy in line.

We had one client back out because we gave them, like, a 3 week schedule for a feature. "We talked to our guy and he said that's impossible." "Impossible? Really?" From some fellow who legitimately had no idea what he was talking about. We ended up demonstrating that we could do the feature, in their office, in a couple of hours to rough out the fundamentals, and they were rather impressed.

Unfortunately, we got them as a client. Very toxic personalities, not fun to work with. But, we were hungry, them's the breaks. The others at the office enjoyed my manifestations of the assorted horrible tragedies I wished upon these people and their families when I returned from a visit. Really awful.

Diagrams.net has been my diamond in the ruff. Small software dev who makes one of the best diagramming softwares I have ever used. It's very intuitive for tech and science people, makes handsome diagrams/workflow/etc., And it's not trying to be a billion dollar company, just a sustainable one.

I worked at a consulting firm (dot com era) with a sales person who told me his job was to lie to customers, and that my job (programmer) was to make him look good. At least he was truthful...