It helps to be in good physical shape when doing archery. Archery requires a lot of back, shoulder and arm strength and it is frequently a surprise to non-archers how difficult it is to pull a bow and hold it steady.
See the post Archery as an Alternative to Weightlifting for more details.
#2. MENTAL STATE
Unless you've been doing archery for years you should probably not be doing archery when you're in a distraught emotional state. Having a bad day at work, an argument with a loved one, etc will dramatically throw off your patience and your ability to relax, focus on the target and shoot successfully.
More experienced archers will be able to relax themselves and can even use archery to help calm themselves down because its comforting for them.
Drinking alcohol doesn't help whatsoever when shooting. It might be fun to drink and pal around with friends, but I recommend throwing a football around instead. Archery requires patience and concentration and trying to do those things while inebriated is a recipe for losing your arrows.
#4. DOMINANT EYE
Do you know which of your eyes is the dominant one? The way to check is to point at something with your finger, hold your hand there and then alternately close one eye and then the other to see which eye is the most accurate. Whichever eye was closest to the target you were pointing at is your dominant eye.
Most people are right-eyed and right-handed, in which case it doesn't cause a problem. Even left-handed people are frequently left-eyed, but sometimes there are people who are dominant in one eye and the hand is the opposite. If such is the case it requires a little experimentation to determine which hand they should be shooting with in an effort to get the most accuracy out of their eyes.
The biggest factor for archery is understanding proper archery form. You want to be standing with your feet at least a foot apart on a slight V angle outwards. Your shoulders should be lined up towards the target and when pulling back on the bowstring your elbow should be raised.
When executing a shot its best to follow an order:
1. Take your stance.
2. Nock an arrow properly.
3. Set your hands.
4. Study the target.
5. Draw the bow and anchor it near your cheekbone.
6. Aim (some people prefer to do this quickly or slowly).
8. Follow through.
#6. FOLLOW THROUGH
The follow through is an often overlooked aspect of archery. It is what happens during the moment you release the bowstring. If you don't hold the bow steady during this critical moment it will cause your shot to go wonky and this is why it is important to have good steady arms.
The bow will want to move forward as the result of the recoil from the string being released. Depending on the bow it may even want to roll forward, which is common for people using Olympic Recurve bows because of the extra weight from sights, stabilizer and V-bar (gadgets which are completely unnecessary and basically act like crutches for people who love gadgets).
The end result is that due to the recoil the bow tends to move during the critical moment of the shot and you want to hold the bow steady even though you've released the shot. Once the arrow is clean away then you can relax your bow arm.
#7. AVOID GADGETS
Archery is a bit like golf in some respects because there is always lots of companies trying to sell some new gadget that is claiming to supposedly improve your golf swing, golf stance, etc. For archery its usually gadgets which claim to make it easier to aim, hold the bow steady, etc. They are completely unnecessary when experience and practice will garner better results. All the extra sights do is provide a frame of reference when shooting. An "Arco Nudo" archer doesn't need the extra sights because they can use imaginary sights in their head to create a reference point based on their past experience and practice.
The only extra thing I would recommend to archers is bow string silencers.
Bow string silencers do two things: #1. Yes, they do make the sound of your bow string rebounding a lot quieter; #2. They also dampen string reverberations. Basically what happens is when the string rebounds it causes vibrations to go up the string and into the bow arms. These vibrations, with time, can damage your bow and weaken it.
So its not something that will improve your aim or anything like that, but they will lengthen the lifespan of your bow by preventing damage to your bow.
I recommend the following books:
Zen Bow, Zen Arrow by John Stevens