The first step in making a pen is deciding what type of pen to make. In general, this choice is between a ballpoint pen, fountain pen, mechanical pencil, or rollerball pen. Within these broad categories, many choices for a penmaker abound. Ballpoint pens can be made as twist pens with one or two lathe-turned barrels or click (retractable) pens which generally have one lathe-turned barrel. The decision here comes down to how much to feature the lathe-turned pen body or the metal components of the pen. Two lathed-turned barrels of course provide more "canvas" for the pen artisan. Rollerball pens generally have two lathe-turned barrels but can be made as closed end pens (no hardware on one or both ends). Mechanical pencils can be made as artist sketch pencils, technical pencils, and shop pencils.
Once the type of pen is settled on, the most enjoyable step, in my opinion, is deciding what material to turn on my lathe for the pen's body or barrel(s). Whether it's going to be wood, stabilized wood, antler, or one of many types of resin, it's fun to give thought to which material will best complement the metal components of the pen for color and overall appearance. Some pens just seem more masculine or feminine, technical or rugged. Each works better I think with the right material. The trouble is the choices are nearly endless. Wood colors are more diverse than you may think and can be dyed or double-dyed to go beyond what is natural. Resins are available in every color or color combination imaginable and with or without things like cast in conifer cones, coffee beans, or computer circuit boards. Beyond wood or just resin there are resin hybrids especially burl-resin hybrids or materials like antler and ebonite.
Next step, preparing the chosen material for turning on a lathe.
