1. You will be safer with zombies. If you don't have decent weapon, a complete med kit set, or unskilled with firearms, then you should stay close to zombies.
2. You will be safer inside buildings. You can detect the enemy position by noise (dots above the npc) and you will be less exposed.
3. Be prepared to fight. Should have at least 4 in aiming skill, an assault rifle, and ammunition.
4. Be prepared to heal. Should have twezeers, needle, bandages, painkillers, line threads for healing bullet wounds.
5. Be prepared to run.
6. Fight with dignity. Crounching will limit your movement reaction (clumsy), stand and fight.
7. Crouch if you really want or need to hide.
8. Don't underestimate the enemies. There are enemies armed with long ranged weapons, assault rifles, shotguns, even pistols could kill you.