Stitch Markers are a wonderful thing. They are small little rings that slide on your needle to mark when you need to switch what kind of stitch you are working on. There are a couple kinds of projects that I don’t really use them on, but for most things when I am working on a special pattern within whatever I am making I make full use of stitch markers.
The two exceptions to my stitch marker rule are when the the pattern you are working on changes every time you work on the right side (like lace or the Saxon braid). On those you just really need to be paying attention.
The other patterns I use, especially for sweaters I use stitch markers, because I an pretty much doing the same thing every time I get to the stitch markers. It makes life less complicated using stitch markers so I don’t have to count, and I don’t have to pay as close attention to what I am working on as I am one of those who can knit and not have to look at what I am working on at every moment.