1: Use non-laminated charts. Much, much easier to fold & unfold.
2: Use a soft pencil. 2B is my preference. It's soft enough to mark the chart and be erased without significantly wearing away the map surface AND hard enough not to wear away too quickly. As a bonus you don't need a different writing tool for your flight record/PLOG, wizz wheel etc.
You also don't have the problem of having to carry some form of dissolving fluid to remove the marker pen ink needed for laminated charts.
3: Trim your charts to remove wasted paper eg the white border, legend etc. You can glue important things such as chart issue number etc either in a sparse area on the front of the chart or on the back.
4. Start with the open chart in front of you. Identify the areas that you don't need to look at in flight for navigation and those you do.
Make sure you include a reasonable buffer around your track line and possible diversion or escape points in your consideration of the areas on the chart.
The general idea is to first fold underneath the areas your not going to need at all, then the areas that are a potential need. That should leave your track and its buffer left.
Concertina the track (if it's a long one) or at least fold away the sections not needed at first.
The idea is that the bits you'll definitely need are displayed, possible bits are only an unfold or two away and bits you won't need are buried deeper.
If you can, it helps to try to keep the folds somewhat symmetrical. It will keep the map thickness somewhat constant which makes writing on it easier.