I am constantly peeling post-it notes off their pads and applying them to my knitting charts. It helps me keep track of which line I'm on (counting challenged me need all the help she can get). The only problem with post-it is that I can't see the previous line. So in order to tell if my stitches are matching up with the previous row I have to stop, peel back the post-it and peek underneath.
The solution? Highlighter tape
There are a lot of suppliers out there, but I got mine at Avid Aviator. 3 rolls for $6.50. With only $3 shipping it seems like the best deal.