Prepare your work surface.
A smooth surface is vital. Any imperfections in your work surface will translate through your paper and mar your calligraphy. Even better than a smooth surface is one that is elevated at a slight angle. The simplest way is to prop a drawing board up with some thick books and work that way, but if you have a slanted desk, even better.
Choose smooth paper.
Just like your work surface, the paper you practice on should be as smooth as possible. Learning on textured paper could be frustrating, as the pen will jump and skip over the rough surface. While textured paper is by no means impossible to calligraph upon, it should be worked up to after a solid foundation has been laid.
Use a protractor to measure the necessary pen angle.
Very seldom (if ever) will you hold the chisel tip of your pen parallel or perpendicular to your base line. Instead, the nib will usually be angled at either 30 or 45 degrees. A good calligraphy reference will show the best angle for that hand, which gives the pen strokes that changing from thick to thin quality, which is indicative of most calligraphy styles.
Locate an example to follow.
Calligraphy books are the best places to look for an exemplar, as they will be sure to give you the complete alphabet to work from. Even a pretty invitation or advertisement from a magazine can give you enough clues to construct the missing letters to create your own exemplar.
Make some practice strokes.
Going back to early penmanship education, letters are made up of specific shapes. While the general shapes stay the same (half circles, straight lines and angles), calligraphy alphabets frequently involve serifs (the little extra flourishes at the beginning or end of a line and in other places) and variations on the basic shapes.
Use a guide with a light box to keep your lines straight.
Placing the guide under your working paper and on top of a light box will keep your lines straight without the need to erase baselines later on.