An airsoft sniper is not just someone in the woods with an airsoft gun. There are alot of factors. You need:
an airsoft gun(obviously)
mask or goggles
some type of camo-ghille suit or hunting clothes
some old army jackets or camoflauge material
a sidearm -mini automatic or spring powered pistol
water & food (only if you are playing an all night match)
and a partner(optional, depending on your own preferences)
please note-some images on this instructable are from airsoft sniper.com-check it out if you have any other questions
Step 1: The Camo
this is probly the hardest part(and most expensive)of this instructable. A ghille suit costs around $150, and I, personally, don't have that kind of money to spend. you need to think colors, if you buy one or make your own. If the area has that yellowish grass and some green grass, make yours the same colors. I would take a picture of the field and use it to match the colors with your bought, or homemade ghille suit. you can make a homemade ghille suit by taking a bunch of old, torn up camo jackets, cut them into little shreds and sew(or even hot glue) them onto a newer jacket. I would even make places for natural vegitation, like sewing a few short dark green threads (maybe an inch long)across the back, and the arm. then take twigs or leaves and stick them into these stitches. Don't forget to do this to the pants and even your gun-unless its a pistol. take the leg of a camoflauge pair of pants and wrap it around the rifle. cut holes for the clip, grip, and scope-if you have one. then do the same thing to it as you did to the ghille suit. building a ghille suit takes a few weeks to accomplish, so plan ahead. Don't assume this is going to happen overnight. also make sure that none of the stitches are loose because you don't want them to start falling off in the field.
Step 2: Tactics
okay, now it's game day, you got your airsoft equiptment and you're ready to play. Now what? well if you are in a sniper team of 2 or more, start to co-ordinate with them. find out what they're wearing so you don't end up shooting them. Plan ambushes along a trail. Usually you put someone with an automatic in front to lead, and the rest follow behind. The front guy should kneel down and put his hand up if he thinks trouble's ahead. The rest of the team should lay down and get ready if he does this, or he starts shooting. if this happens, don't panic and run, this would defeat the whole purpose of an airsoft sniper. stay hidden until they get close. They will think that there was only one guy, and he ran off. then waste em. Stay down, don't get up unless you are behind cover. this tactic is one of the more dangerous ones, and you might get hit. If you are cautious,alone,accurate and patient you can pull off long range shots. Practice with your gun. make sure you are dead-on, every shot. wait for the wind to stop before making the shot. you might have to wait an hour or longer to accomplish a great shot like this, so you got to be patient. find a good vantage point. if there is a trail with trees, branches, and bushes about 10-20 feet away, this is your spot. make sure you can move inside a spot like this without making too much noise or risk being seen. then you got to wait a long time, until someone walks into the sights of your gun. I would try bolth ways to find what you're best at.
Step 3: Movement
to move silently, you need shoes. Boots are too big, but they keep your feet dry. I'd wear these in muddy conditions, and if i was going to wait a while to take a shot. For shoes, you can't wear white or other bright colors. I have devised a solution to this. Take a strip of material off an old camo jacket and wrap it around the sides of the shoe, kind of like a moccasin. take hot glue and seal it at the end, and put a stitch across the bottom from side to side. don't glue the material to your shoes, unless they are an old pair, and don't put material on the bottom or else you wouldn't be able to take it off. to take it off, just take off your shoe and slide the material off. please note this is only a temporary fix. anyway, you need shoes to be quiet. to walk, step down on your heel and roll the side of your foot down. move slowly always. don't move fast unless you are being chased by the enemy. when you walk, don't put your gun in the shooting position-it restricts your field of vision to whats in the sight. point the gun down at an angle, and constantly look around and listen. don't talk to your teammates, and tell them to be quiet too. you need to listen for gunfire, talking and movement. This is the best way to locate the enemy position. if you crawl, you should be near the enemy. dont crawl unless you are close, and when you do crawl, you must go SLOW. an inch in 5 seconds. it should take 5 minutes to move 100 yards. also crawl with your gun underneath your stomach so the enemy cant identify you by your gun. when they look at you, dont move. when they turn their back, pull out your gun and shoot.
Step 4: Extras
I hope that this instructable helps on your next game.(go to the site i mention at the beginning for a ton more info.) you can also plant traps on the trails that you hide by. this can start your ambush if you plan one. I heard that if you take those party popper things (you know, the ones with the pull string and the confetti) and carefully take off the cardboard on the end. then take out the confetti, and fill it with airsoft bb's. then put the carboard back on and tape it to a tree. finally, attatch the string to fishing string and put in a nail so it hooks around and attatch it to another tree across the trail. I haven't tried this yet, but it looks like a good idea. there is another instructable on this site that explains more about it. anyway, good luck on your next game, i hope this helped. happy hunting!