If you purchase a used bow it will most probably come with everything ready to hunt.  But with older bows particularly you may want to replace some of the accessories to increase functionality.  The bow sights are probably the most important to upgrade.  A good fiber optic sight is almost a necessity for deer hunting since you are most likely to see deer at dusk.  Fiber optic sites

gather light over a length of special plastic and transfer it to a point on the end of a plastic rod.  This point of light, your front sight, will show up much better at dusk than simple pin sights.  The longer the fiber optic plastic, the more light gathering capability it will have.

For a rear sight, a peep sight which is installed in the bow string is the common solution to shooting well without a lot of practice.  For hunting you should use the largest peep, at least 1/4" in diameter, to let in the most light.  The bow string strands are separated so that equal numbers of strands traverse each side of the peep, the peep is adjusted in height to fit your eye, and then serving (strong thread) is wrapped around the string above and         below the peep to hold it in place.  There are two types of peeps.

One type is inserted into the string with the hole parallel to the string.  This type allows you to  see through the hole  only when the bow is drawn.  The second type fits into the string with the hole pointing

toward the front of the bow.   Since the bow string has a tendency to rotate when the bow is drawn, a rubber band or tube attached to one of the bow cables is employed to keep the hole pointed toward the front of the bow.

The next important accessory is the arrow rest.  You should have one that lets the arrow pass over or

through it without touching the arrow's fletching (feathers or plastic vanes).  There are many types of arrow rests that fulfill this  requirement.  The simplest is the arrow rest with two prongs that hold the arrow in such a manner that the "cock feather" passes between the prongs.  The cock feather is the different color feather or vane.  If you use this type of arrow rest be sure the arrows you purchase have nocks that are oriented

right or are adjustable because the usual preassembled arrows point the cock feather horizontally away from the bow riser, not down.  A disadvantage of this type of arrow rest is that the arrow can be easily knocked off the rest in drawing the bow. Either a drop away arrow rest with a deep "V" (guides the arrow through part of its travel through the bow, but drops away before the fletching reaches the V) or a Whisker Biscuit arrow rest works better for hunting.  The Whisker Biscuit is a

circular brush that holds the arrow securely, but allows the fletching to slip between the bristles.  Both hold the arrow securely, although the Whisker Biscuit will slow the arrow a little bit relative to the drop away.

To shoot accurately you need to do everything exactly the same for each shot.  An accessory that can

help you do this is a mechanical release.  If you let the bow string slip off from your fingers when shooting, it is hard to be totally consistent.  The mechanical release, or trigger release mechanizes the release, and just as machines are usually better than people at doing repetitive operations, the mechanical release will help you shoot more accurately.

 The next accessory is the stabilizer.  It dampens vibration set up in the bow when the string is

released.  Shooting a bow is not much different from plucking a guitar or violin string, except that the displacement of the string is much greater.  Therefore the shock upon release is much greater.  The stabilizer helps to dissipate that shock.  This helps to silence the bow and makes it more comfortable to shoot.  It also puts weight in front of the bow to help balance the bow in your hand.

The last common major accessory is a quiver for carrying arrows.  Most bow packages come with a quiver that attaches to the bow for carrying.  It mounts on a plastic block that attaches to the rear of the bow sight.

An accessory that allows people of lesser strength to participate in the sport of archery is the drawlock.  It is a device that attaches to a bow which allows the bow to be drawn in an unconventional manner using the stronger muscles of the back.  It also  maintains the bow at full draw, has a trigger release, and a safety.  In operation it converts the compound bow into a vertical crossbow, and is an alternative to the crossbow.  A number of states limit the use of a drawlock for hunting to those who have a disability or to people over 65 years of age, Michigan being one of them, but they are legal in quite a number of states.  A new drawlock product that is a "bowhunting system" has recently reported that is ideal for bowhunting from a tree stand.  Although not yet available for sale, it is described and demonstrated at http://www.bowdrawlock.com.