Players with -2.0 or worse cannot enter 1.0 systems
Players with -2.5 or worse cannot enter 0.9 systems
Players with -3.0 or worse cannot enter 0.8 systems
Players with -3.5 or worse cannot enter 0.7 systems
Players with -4.0 or worse cannot enter 0.6 systems
Players with -4.5 or worse cannot enter 0.5 systems

Amarr = Radar (hacking)
Caldari = Gravimetric (mining)
Minmatar = Ladar (gas)
Gallente = Magnetometric (salvaging)

Teamwork: giving the enemy others to shoot at