I do the same as
@bulkbiker. It is time-consuming and also somewhat confusing initially, but gets much easier over time.
To start with the confusing thing for me was that the grams of carbs (on the food labels) are usually listed as "per portion" so you need to check the label to find out what a "portion" is. This may bear little resemblance to what you, personally, would consider to be a one-person portion. Or, it might just list carbs "per 100 grams."
There are also lots of foods that don't have nutrition labels attached to them at all. Fresh fruit and veg. Alcoholic drinks. And so forth. For those, I type the name of the food into Google, followed by the word "nutrition" or "carbohydrate."
Another valuable resource for (general) information on which foods are low-carb or high-carb is
https://www.dietdoctor.com/low-carb. This was, for me, the most useful such resource when I first went "low-carb" (but I had not found this forum yet).
Of course
@Guzzler is right that none of this makes much sense until you decide, first, what level of low-carb you are aiming for. There is a description of the range of possibilities here:
http://www.diabetes.co.uk/diet/low-carb-diabetes-diet.html.