I would ask my lead engineer how they want these prepared. Look for some examnples in the files, take it to them and ask them if these are a suitable template.
In general, a calculation note (I'm a process engineer so bare that in mind) would state the client, project, date, object of the calculation. I'd like to see a short summary how you are doing it, that whoever is checking your work has an idea of your methodology.
Include references for both methods and data. There is always some grey area here what needs to be referenced. Do I as the checker need to see a reference that the boiling point of water at 14.696 psia is 212F? No. However, things like flows, pressures, temperatures, physical properties should be referenced where they were taken from including what version (simulation models change, a set of stream properties, can change (maybe a lot, maybe minor) from run to run depending what else is changing.
Finally, a conclusion/recommendation. For example, if you are sizing a line for me, I want to see a recommendation "a 14" line is recommended" and any necessary discussion why that size is picked if it's not obvious from your calculations. By the time I get to that point, I've followed through your calculations so it should just be a check off that I agree.