It's hard to know where to start when commenting on the One Paseo DEIR. Fortunately, the City provides this handy List of Issues for Community Plans. It's a bit confusing, but if you scan through the list, you'll see things like "review of vehicle and pedestrian circulation patterns for safety", "adequacy of parks and other public facilities", "potential truck traffic impacts on surrounding streets", and "appropriate level of density."
Once you have an idea, go to the DEIR Document Page and see if you can find the appropriate section that might talk about your issue. Sometimes important information is in an appendix, feel free to skim looking only at headlines, tables and charts!
If you want to get into a bit more detail, look into the City's General Plan web page (scroll down to "General Plan 2008".) This page has additional documents on the requirements the project is supposed to meet. Surprisingly, the General Plan documents aren't very long and are fairly readable! Some interesting ones are the Land Use & Community Planning Element, which talks about the City of Villages, the Strategic Framework, which is a nice overview, and the Urban Design Element, which talks about how cities are supposed to be built.