This is one of the most useful tools in our human factors toolkit. In the right hands you can learn so much about existing tasks and future tasks when considered during design.
Here is the job aid I used for carrying out task analysis. Includes a guide for scoring tasks to rank them by criticality (add the scores for each criteria and the highest is the most critical), a prompt sheet for human error analysis and list of Performance Influencing Factors https://abrisk.co.uk/wp-content/uploads/2023/03/Task-risk-management-job-aid06.pdf
In April 2023 the Chartered Institute of Ergonomics and Human Factors (CIEHF) published a guidance document on how to carry out human factors assessments of critical tasks. I was part of the creative team that developed the content. Following this publication I have made a few tweaks to the template I use for my task analysis reports. You may find this useful for your own reports. I am sharing the Word file so you can copy-paste it into your own template.
In 2021 I presented as part of a Task Analysis Masterclass webinar organised by CIEHF. You can view my slide pack with notes.
Other resources you may find useful:
I am still a strong advocate of the approach to Safety Critical Task Analysis presented in the Health and Safety Executive (HSE) report OTO 1999 092 – Human Factors Assessment of Safety Critical Tasks (I was lead author). It used to be a free download from the HSE website but this is no longer the case. You can download a copy at https://abrisk.co.uk/wp-content/uploads/2023/09/OTO-1999-092.pdf