Where can I get nutrition info?
Wherever possible, you should get the serving size and macro information from food labels. So, for example, if you have a bowl of yogurt you would record the serving size (1 cup, 245g), the macros (12.1g protein, 19.1g fat and 9.1g carbs) and the time that you ate (between 8am and 11am) in your food log. Remember you need to adjust your serving size and macros based on what you actually eat, so for example if you actually ate 350g of yogurt you would record a serving size of 1.4 (350g / 245g = 1.4) and adjust the macros accordingly (17.4g protein, 26.7g fat and 12.7g carbs).
If you are cooking then you need to log every ingredient that goes into your meal. So weigh out the serving sizes using kitchen scales and then add up all the ingredients to get the total data for your meal. If you are eating prepared meals, then just use the food label which shows a summary of what you ate. Ideally you want to be as granular as possible so you can see how the various ingredients are contributing to your macro targets. Whilst it takes a few extra minutes to record all this, once you your ingredients saved you can use them for future meals. And after a couple of weeks you will be able to guess serving sizes sizes without need to weigh food or check the food labels.
One area of note is around net carbs. Accounting for the energy in fibre is an on-going debate. On most food labels, the grams of dietary fibre are already included in the total carbohydrate count and calculated as 4 calories per gram like any other carb. However, certain people attribute zero calories to fibre since your body’s digestive enzymes can’t break much of it down. This leads to the concept of “net carbs” which are the total carbs minus fibre (and artificial sugars). Since there is no general consensus on how much energy should be attributed to a gram of fibre, you should fiber in your total carb value and attribute it 4 calories per gram. Be aware that fiber is included in the Total Carb figure on American food labels whilst it is separate on European and Australasian food labels and so will need to be added back.
It is important to keep an eye on your serving sizes and double check the food labels as these sneaky food manufacturers will often only provide you with half or quarter serving sizes on their food labels. Also you may find a bit of inaccuracy in food labels (for example manufacturers can round to the nearest 0.5 grams with fats which means this is not always precise) but this should not have an impact on your performance.