I believe you and would be interested in your list of things that matter?
- Getting the requirements right. This by far has the most impact on effectiveness
- Reducing friction. Simple things like proficiency with high quality tools, smooth and fast builds, clean logs, easy ways to generate and analyze core dumps, accumulate to produce an outsize effect on productivity.
- Uninterrupted, substantial blocks of focused time. It is staggering how easily chat, email and meetings can destroy productivity.
Open plan, with 2nd line support talking to customers right next to developers.
Quick tip: For people who work in a company where they don't necessarily have control over their own time: schedule the living out of your calendar. Book endless meetings with other programmers, then just sit there and do work. "Q2 Backend Architecture Review: 4 hrs" can just be a few people sitting in the meeting room programming. It's crazy the power of blocked out time on your calendar to a manager who otherwise sees an empty day.
Another way I've tried to tackle this is on day 1 of a job - I've blocked out a huge chunk (4 hours) of my daily calendar of "Coding Time - No Meetings, No Slack, No Email" before anyone could tell me no.
My team has coordinated it so we spend mornings working independently on the most important things we need to get done. Only the afternoon is open for meetings. In those meetings we often identify things that we will each work on independently the next morning. This better planning leads to more focus and the reduction in distractions leads to more productivity.
Emergencies are exceptions, but it's amazing how rare those can be if everyone has a decent amount of time to handle their most important things every day. Also, many people are not well organized and this small amount of organization makes a massive difference.
I don't think I quite captured everything, I might take another shot at this again sometime.