Loss of Tail Rotor Effectiveness
This is sometimes known as tail rotor breakaway, or a stall, which is not strictly correct, as thrust is still being produced – it’s just not enough for the task in hand. It shows up as a sudden, uncommanded right yaw (with North American rotation), and has amongst its causes high density altitudes, high power settings, low airspeeds (below about 30 kts) and altitudes, and vortex ring, not forgetting turns in the opposite direction of blade rotation. Your helicopter will be more susceptible to it if the tail rotor is masked by a tail surface, like a vertical fin, and it can be especially triggered by tail and side winds (this is actually a significant reason for maintaining main rotor RPM – as the tail rotor runs at a fixed speed in relation to it, lower NR will reduce tail rotor effectiveness in proportion). Recovery in this case comes from a combination of full power pedal, forward cyclic and reduction in collective, or autorotation. Prevention lies in keeping into wind and always using the power pedal (left in a 206 or one with similar blade rotation). If you use the other one, not only will the fuel governor ensure that the aircraft will settle after a short time (using the power pedal by itself makes it climb), but a large bootful of the power pedal in a fast turn the other way will create a large torque spike.

Jammed Controls
Aside from jammed tail rotor pedals, discussed above, your cyclic or collective may jam as well. Both cases will result in a run-on landing. To get out of a jammed collective, just bring the speed right back. This will cause you to descend, and you can use your speed to aim at the ground. Hopefully, your cyclic will jam in the centre. Anyway, leaning in the desired direction (passengers as well) will cause enough of a shift in C of G to turn the ship in the desired direction.

Hydraulic Boost Failure