There are also many types of calligraphy, such as modern calligraphy that uses brush pens. There are also types of calligraphy that use a pen that has a metal tip that you dip in ink and then write. Both work well, so definitely try both.
Now back to making thick and thin lines. How to create these thick and thin lines all matters on pressure and direction. When the direction of your writing is going up you apply little pressure to make a thin line. When the direction of your writing is going down you apply more pressure to create a thick line.
to create thick and thin lines go to beginner hand lettering tutorial