It's VERY easy to lose track of rows so finding a method that works for you is important.
Here's what I do:
If the pattern has something like cables, decreases, or increases that you have to do on specific rows I write out the numbers of rows and and make notes on them and then mark them off as I do them. Kind of like this:
If it's merely keeping track of rows I either right down numbers and mark off each one or I write a number each time I do a row. On some patterns keeping track makes no difference because the pattern is easy to see or the pattern tells you to measure in inches instead of rows.
I prefer the pencil and paper method to the row counter..I can get more info in.