Regardless of project&#x2F;planning methodology, having a ever-growing checklist of less-obvious estimation items is a simple way to avoid forgetting to consider them. The book &quot;Software Estimation: Demystifying the Black Art&quot; [1] by Steve McConnell contains a number of these.<p>Some examples:<p><pre><code>  - Team or company meetings
  - Team member sick days, holidays, vacations
  - Bugs in third party software
  - Maintenance of previous systems
  - Maintenance of build automation
  - Demos
  - Interviews
  - ...
</code></pre>
... or your own list of whatever other items you have historically forgotten, or tend to forget when estimating.<p>In the painting example, the moving of the furniture was something I overlooked, despite having made the effort to carefully think of all tasks. A estimation checklist built up from previous painting projects could have triggered me to consider this task.<p>[1] <a href="http:&#x2F;&#x2F;www.amazon.com&#x2F;Software-Estimation-Demystifying-Developer-Practices&#x2F;dp&#x2F;0735605351" rel="nofollow">http:&#x2F;&#x2F;www.amazon.com&#x2F;Software-Estimation-Demystifying-Devel...</a>