Great (succinct) list of GnuPlot tricks

http://sparky.rice.edu/gnuplot.html

For example:

Point size and type

• pointsize is to expand points: set pointsize 2.
• type 'test' to see the colors and point types available
• 
  

lt is for color of the points:

• -1=black
• 1=red
• 2=grn
• 3=blue
  
• 4=purple
  
• 5=aqua
  
• 6=brn
  
• 7=orange
  
• 8=light-brn
  

pt gives a particular point type:

• 1=diamond
  
• 2=+
  
• 3=square
  
• 4=X
  
• 5=triangle
  
• 6=*

(and, for  postscipt: 

• 1=+,
  
• 2=X,
  
• 3=*,
  
• 4=square,
  
• 5=filled square,
  
• 6=circle,
• 7=filled circle,
  
• 8=triangle,
  
• 9=filled triangle,
• etc.