If the enemy is in range, so are you. Incoming fire has the right of way. The easy way is always mined. Try to look unimportant, they may be low on ammo.
Professionals are predictable, it's the amateurs that are dangerous.
When you're ready for them. When you're not ready for them. If you can't remember, the claymore is pointed at you. If your attack is going well, you have walked into an ambush. Don't draw fire, it irritates the people around you.