When I started, I made a database of the foods I eat most regularly and charted the values - carbs, protein, fat. My husband and I tend to eat clean keto and eat a lot of the same foods, over and over (meat, pepperoni, cream, eggs, mayo, bacon, some cheese, some veggies. Now I know from that how many carbs are in the common things that I consume.
It isn’t difficult for me to keep my carbs low as I prefer rich foods to veggies. When I do make veggies, I add a lot of butter, MCT oil or bacon grease, or salad dressing.