Materials
Before jumping right in, it's in your best interest to collect the right materials beforehand. Some suggestions include...
Now I'm going to tell you the key rule to the technique: every up-stroke is thin, and every down-stroke is thick. So, every time you move the pen towards the top of the paper, the stroke must be thin; every time the pen moves downward, the stroke is a lot thicker.
If you want a visual reference, watch the 6-minute video below on how to practice basic lettering. Captions are available if you need them. Here's the link to the video: How To: Calligraphy & Hand Lettering for Beginners!