You can use obstacles to your advantage. Throw grenades against obstacles to deflect them around corners. Stand close to cover so that you can shoot through it while still being protected from distance gunfire. Kick an enemy or use a well placed explosion to make it fall into a hole. Some obstacles can be destroyed by explosions and may reveal hidden items.

Type of obstacle Blocks Movement Blocks Visibility Blocks Projectiles Blocks Thrown Projectiles
wall yes yes yes yes
window yes no no no
cover yes no yes, blocks based on distance no
hole yes, unless moving faster than normal no no no