Tape a piece of mat board or cardstock to the table with temporary adhesive to protect it from stray pen marks. If you're worried that the tape will leave sticky residue, use a large piece of butcher paper that you can wrap around and affix under the table. You can also use the paper to jot notes, sketch projects or doodle if you're bored.
Use a small self-adhesive mat when you need to work with a craft knife or other cutting tools. If you'll be doing it often, consider protecting the table's surface completely with a board cover that you can clean with a damp cloth (see Resources).
Add a tray to the side of the table to hold tools. In addition to being convenient, it'll also keep you from having to juggle your pens or placing a space-hogging tool caddy on the table that might also scratch the surface (see Resources).
Keep pens and cutting tools capped tightly when not in use. Otherwise a simple bump of your elbow may stain or cut your table, clothing, chair or floor.
Choose a floor lamp when looking for a studio light fixture. If you use a version that clamps onto your drafting table, it may leave a permanent indentation if you decide to remove it later (see Resources).
Cover with the entire drafting table with an old tablecloth, drop cloth or piece of plastic if you won't be using it for several days. In addition to keeping dust off the table, it will also help protect your drawing and cutting tools.