Okay, if you are snacking a lot it's tricky and you need to be detailed.

Might have mentioned it before, my system is easy.

I just write down the date, and the hundreds of kcal rounded to nearest. So for example

04.10. 4+6+2+3+1

In this example the 4 is the 400 from a Muffin in the morning, the 600 is from chicken with vegetables and cashews at noon, the 2 is a doughnut in the afternoon, 3 are the protein bars after training, and 1 are two pieces of chocolate in the evening. That would be 1600kcal total which is on the low side for my needs.

I can either guess or already know from memory most "standard meals".

Now if you are snacking a lot in between, then you'll have lots of small 100kcal or even 50kcal bites. I sometimes just make a note in my head, for example on pieces of chocolate, and write them down next time I walk by my paper sheet.