I've reached the point (long past, actually) where I need to review all the data I've already collected to look for things that I passed over when I was first starting out seven years ago.
One thing I've noticed as I get acquainted with Ancestral Sources (previously I was using Gedcom Census) is that AS is prompting me to double-check the other names on the page as I do each entry, so I can tell AS what fields to carry over for the next census entry. This is a good reminder not to neglect the fact that I have two brothers living next door to each other, or cousins in the same apartment building.
Another thing I'm trying to do as I re-enter data is to work in batches -- records from the same census year, or a group of obituaries or birth records all belonging to the same siblings, and so on. The patterns in the data make themselves more evident that way. If I notice that I have records from all the siblings but one, I add the other one to a Named List to remind myself to look for the missing data. Some people use checklists, and I may start doing this as well, either by making use of the blank forms in Emily Anne Croom's Unpuzzling Your Past, or by creating digital equivalents in Excel and linking those into Scrivener.
What other things about handling evidence have proven to be helpful for you?