There are quite a few defensive airsoft tactics. This one is on the theory kill or be killed. Instead of waiting in a position for an enemy to come by(which may not even happen) try going and finding your enemy. This will create confusion on the attacking team and will leave them retreating and or being laced up.
Step 2: Defensive tactic 2
I named this tactic Black Hawk. The defending team (depending on team size) will place 4-5 teamates in trees lining a path or commonly walked area, and send other teammates(preferably fast runners and maybe a fat kid) to lure the attacking team into the ambush area they will take positions under the trees that contain a "black hawk" remain hidden until majority of the attacking team is in the zone. The problem with this tactic is that if the attacking team sees the "black hawks" in the trees it could be very deadly for the defending team but if this is performed correctly it will result your team with another victory. Remember you have the element of surprise use this to your advantage.
Step 3: Sniping positions
Snipers can be verrryyyy deadly in airsoft. A snipers ideal location is always somewhere up high where he can see most of the playing area. Snipers should not be directly with the rest of the defensive positions but rather off behind and over to a side. One spotter should go with the sniper for an extra pair of eyes and ears and help incase the sniper gets ambushed. If the playing area is realatively flat and the trees are too dense to be a reliable high point be ironic and set up in a hole at the end of a trail. Wait for an attacker to get in range then pick em' off as they come.