I won't say that practice makes you perfect, but I will 100% stand by "practice makes pretty!"
I tell my calligraphy students that the best way to practice is write a whole entire sheet of the same letter in different ways. Then, choose your very favorite version on the sheet, and then start from there and try to replicate your best one! That's how I developed the signature calligraphy style that All She Wrote Notes is known for today.
Whether you are a beginner or a more experienced calligrapher that wants to fine tune your skills, here are my favorite practice papers.
The Borden & Riley tracing pad is great when you need to see through the paper, but I also love the Rhodia pad because it is smooth and thick paper that's perfect for practicing. Both of these are available at Paper and Ink Arts.
When I sell my work, I typically use at least 110 lb card stock.