I draw a course line in permanent marker, leaving gaps for navigational features. To one side of the track I draw a large wind arrow. I circle airfields if I'm landing away. I also mark parachute sites & anything NOTAMed with a black circle & a cartoon to remind me what it is.
To clean the chart I keep a little bottle of AVGAS - when I do a fuel check I top the bottle up rather than throwing the fuel away. It smells nice and it's free (ish).