Identify by helicopter characteristics

The fuselage of the S-70/H-60 family has an air foil profile shape, when viewed from the side. The bottom is nearly flat, while the top is rounded, with the highest part near the rotor mast. The four blade tail rotor on the right of the vertical stabiliser is a bit canted, and the single piece horizontal stabiliser can tilt in a cut-out of the vertical fin. It has a fixed tail wheel gear, of which the tail wheel can have one or two wheels and can be at different locations.

The S-76 is a streamlined helicopter with a fuselage that smoothly tapers into the tail boom. It has a retractable gear, of which the main gear retracts rearward in the fuselage.

This helicopter has a four blade main rotor, powered by two turboshaft engines placed at the side of the gear box housing. Typical for the S-92 are the canted, four blade tail rotor on the right side, the single horizontal stabiliser, attached to the vertical stabiliser by a rodd, and big sponsons at the sides of the fuselage.

This medium size helicopter comes in many versions, all of which have in common the two engines placed on top of the fuselage, in front of the main rotor with exhausts at the side. The single or double wheel main landing gear retracts in small stubs or larger sponsons. The nose gear has two wheels as standard. The tail rotor is mounted at the right top of the vertical stabiliser, with a horizontal stabiliser on the opposite side. 

The Gazelle was one of this first helicopters with a shrouded tail rotor. Additionally, it has a droplet shaped fuselage, on top of which the engine is slightly separated from the (rear) fuselage. The helicopter has a three blade main rotor, and skids with standard tubes. 

The Alouette II & Lama are composed of three elements: a framed, dome-shaped cabin with a lot of windows, the middle with fuel tank and an uncovered engine on top, and an open framework tail boom. The helicopter has a three blade main rotor and two blade tail rotor, on the right. Most have skids as landing gear, but some have a four leg wheeled gear.

The Alouette III retains the exposed engine and basic rotor system of the Alouette II, but for the rest it is different. The wide, rounded cabin and fuselage form one entity with a lot of windows at the front. The tail boom is covered, and the Alouette III has a fixed tricycle gear. The helicopter has a three blade main rotor and three blade tail rotor, on the right.

This helicopter is quite similar to the Leonardo AW139. However, the T625 has a more rounded side of fuselage and tail boom (no 'body line') and has end plates at the tips of the horizontal stabilisers. Other differences are much smaller. 

Essentially, the Westland 30 is a Westland Lynx with a larger fuselage. It sits close to the ground with its fixed gear, that has single wheels on the main leg and two on the nose leg. Other features are five square cabin windows and horizontal stabilisers with large end plates close to the tail. (photo: Peter Bakema/WikiMedia)

The best way to distinguish the Lynx or Wildcat is by looking for the long rounded nose and the tail boom that is somewhat pointing down. The Lynx can be fitted with skids or a wheeled gear. In case of wheels, the two main gears can be tilted around the vertical axis, to make the Lynx unable to move, but the heli can still taxi on its wheels when they are tilted right.