Agile: Planning Poker

https://www.planningpoker.com/

Estimation Process and related artifacts

Your QMS could include a process on estimation (that presents the estimation techniques and the associated activities to be executed in order to produce the final estimation sheets that are input for ROMs, Proposals, Change Requests, ...).

One example (INTERNAL):

• https://quality.critical.pt/qmsunified/SUP-support/SUP-09-estimation/CSW-QMS-2010-PCS-00878-estimation-process.pdf#search=sum%20up%20xls

Some common artifacts include templates and models to help you estimating (INTERNAL, use the QMS Portal with the doc id enclosed in double quotes):

• Estimation form (template): CSW-QMS-2011-TPL-02102-estimation-sum-up.xls (now a xltx)
• Planning Poker form (template): CSW-QMS-2015-TPL-02398-planning-poker-estimation.xltx
• Effort Per Phase Model: CSW-QMS-2009-DOC-04974-effort-model-2014-baseline-data4all.xlsx
• Safety Critical Estimation Model: CSW-QMS-2014-DOC-01296-asd-estimation-model.xlsx
• Estimation @ CRITICAL Software - Study on the Estimation Process for CRITICAL Software Projects: CSW-ESTIMATE-2009-PCS-00707-estimation-process.doc

PS. If you're interested in estimation models, google for them. They are very dependent on the business you're working on although there are some attempts to generalize them. 

Example: COCOMO Estimation Model.