There is lots of good advice here, but I'm always amazed that these articles miss the #1 improvement to estimates recommended and validated by scientific studies: do not estimate in units of time.
Everything else here applies, but don't estimate in time. Estimate in difficulty points, t shirt sizes, cups of coffee, gold stars, anything will do. Then as you track your outcomes (see TFA), measure the average relationship between your units and time. Then use that relationship to project a timeline based on your gold stars or whatever.
Using the law of large numbers to average externalities and developer inaccuracy into your time estimate has been the most accurate method since Kahneman and Tversky's Nobel prize winning studies in the 1970s.
Everything else here applies, but don't estimate in time. Estimate in difficulty points, t shirt sizes, cups of coffee, gold stars, anything will do. Then as you track your outcomes (see TFA), measure the average relationship between your units and time. Then use that relationship to project a timeline based on your gold stars or whatever.
Using the law of large numbers to average externalities and developer inaccuracy into your time estimate has been the most accurate method since Kahneman and Tversky's Nobel prize winning studies in the 1970s.