Estimating should be done in a very orderly set pattern, so that you are sure you have covered everything, that is important and associated to what you are taking off regardless of what it is. I usually start with the specifications taking notes, and making a list of what I am looking for, that are to be used with regard to brands and materials, that the architect wants and specifies are to be used on that particular project. Some specifications are generic and don’t vary much from one project to the next and vary greatly and all need to be taken seriously regardless as the are what govern the project and cannot be changed or varied from unless the architects puts it in writing and makes it a addendum to the specifications. I personally try to setup a starting point and work all the way around the project till I get back to the point that I started and then going back checking my notes and list to make sure I haven’t missed any thing. This holds true regardless of what to takeoff whether it be concrete, masonry, structural metal, cold formed metal, wood, insulation, roofing, doors & windows, drywall, floor finishes, painting, acoustical ceilings, plumbing, heating and air, electrical, in other words you simply follow the pattern regardless of what you are working on it stills holds true. By getting in the habit of doing takeoffs in the same order each time, it allows them go faster and you feel more confident that you have covered everything to your best ability regardless to the size of the project from the smallest to very large projects.