I don't use any method for marking the chart. I find marking distracting. I tend to forget doing it at the end of the row and then it gets really confusing.
I just look at the project as a whole and then the last knitted row and figure what I did on it and then find that row from the chart. Even with large lace charts you usually remember whereabouts in the chart you should look. For me this method seems to be faster than marking.
I might be a compulsive hand washer, but to me using a marker or a post-it near a project is a frightening idea. My fingers would feel sticky and I would have to go and wash my hands after every mark. Magnets would not have that problem, but I like to see the previous and next rows on the chart and the strip would cover them.