The best choice for most purposes is a pneumatic graver. This is an affordable tool that fits in the palm of one hand, and uses air to drive the point into the metal. Gravers come with many different shapes of tips, but a square "V" cut point is a good versatile option to start with. If this is your first engraving project, you might want to stay away from that heirloom watch. Practice on an item that you won't mind damaging. A softer metal such as copper or some brass alloys will be faster and easier to engrave than steel or other hard metals. Use a damp cloth to clean the surface of the metal, then a dry cloth to remove the moisture. If the metal is still grimy, scrub it with soapy water, then dry. If the metal is coated with a protective finish, which is often the case for brass, you do not need to remove it. However, the engraving process will cut through this finish, so you'll need to apply a new finish afterward if you want the metal color to remain consistent. If you are working on a small object, or engraving for the first time, draw or print out a design that has simple, well-spaced lines. Finicky, detailed work is difficult to do without practice, and may end up looking muddled or blurry once engraved. You may be able to draw the design directly on to the metal. If not, draw or print it out at the correct size, then follow the next step to transfer it onto the metal. If engraving letters, make them as even as possible by drawing them between two straight, parallel lines drawn with a ruler. Follow this step if you want to transfer a design onto the metal; if it is already on the metal, move on to the next step instead. If you cannot find the specialized materials necessary, search online for one of the many other ways to transfer an image. Note that most of these also require some type of specialized equipment.  Add a varnish or shellac to the area you want engraved, waiting until it is mostly dry and slightly tacky. Draw the design onto polyester film (Mylar) using a soft lead pencil. Cover the drawing with scotch tape. Rub the tape thoroughly with your fingernail or a burnisher, then carefully lift up the tape. The design is now on the tape. Stick the tape over the varnished metal. Rub it in with your fingernail in the same way, then remove it. Engraving will be much easier if you use a clamp or vise to prevent the metal from slipping. You may use a handheld clamp that allows you to hold it in one hand with a steadier grip, but be aware that this increases the chance of cuts or scrapes. If you are using a powered tool, or a hammer and chisel that requires two hands, a clamp holding the metal to a table or other stable surface is highly recommended. Use your chosen tool to turn the drawing into an engraving, putting pressure on the point at an angle to chip away pieces of metal. For your first attempts, try to keep the end of your tool at the same angle throughout the engraving. Begin by working a straight line in both directions until it is a noticeable, deep cut. Use this as a starting point to move on to the remaining lines. To engrave a line with a complex shape, such as a J, finish the straight portion first. Once this is complete, move on to the more difficult non-carved section. Engraving is an art form that people practice and improve upon their entire lives. If you are interested in new techniques, machine engraving, or practical advice on expanding your set of tools, there are many resources available:  Search for "engraving forums" online to find communities of engravers. If you are interested in a specific type, you may be able to find a forum or subforum dedicated to precious metals, steel, or other types of metal engraving. Find books on engraving. A book on engraving will likely go into more detail than you'll find online. If you're not sure which book to start with, an engraving forum may be a good place to ask. Study with local engravers. This might mean enrolling in a community college course, or finding a local engraving studio that holds one-time workshops. If you're serious about continuing in the engraving world, consider offering free labor to apprentice with an engraver, or enroll in a one-year engraving program.

Summary:
Get an engraving tool. Choose a metal object to practice on. Clean the metal. Draw or print a design. Transfer the design onto the metal (if necessary). Clamp your metal in place. Cut into the design. Learn more.