Good advice already given all round on this one. However, I would add that the definitive answer lies in the emergency drills in the POH or approved checklist for your type of aircraft. The immediate actions should be memorised, followed by the "what's up" which (if time permits) can be actioned from the checklist.
I would personally favour a formalised approach, since the variables that "Fireflybob", (quite rightly), considers, can still be covered.
>> inserted: Lest I forget, during practice don't forget you are
NOT absolved from the low flying rules: in particular "Not within 500 ft of any person, vehicle, vessel or structure except when taking off or landing according to normal aviation practice."
This means that unless you are conforming to the normal traffic pattern of an airfield, and are making standard calls to that airfield, and (if a controlled airfield) you have received clearance to land, you
MUST plan to go-around at or above 500ft agl.
Of course in a real emergency the low flying rules do not count, but don't forget to scan the approach for obstacles.<<
In general I was taught that an engine failure is followed by the immediate actions and then the silent question, "Is there any sign of fire or mechanical failure?" This question can be verbalised to the instructor / examiner since he is setting the training scenario, but in real life should be the first question which enters your mind.
The answer to the silent question determines your following actions:
In general, the immediate (memory) items would be:
Carb Heat
ON
Select the attitude required for best glide speed
(Vg)
Select a field within a distance equivalent to an arc drawn from where the nose would be in the normal straight and level attitude, around to the wingtips and turn towards it:
(In choosing a field, use the 5 "esses")
Size
Shape
Surface
Slope
Surroundings
Another two I would add are:
Sheep (or cows etc)
Survivability (land near habitation if possible)
While selecting and turning towards the field, ask yourself the question,
"Any sign of fire or mechanical failure?" As CFIMEI quite rightly points out, divide your attention inside and out, and above all maintain control of the aircraft. Don't forget the 3 golden rules "Aviate, Navigate, Communicate", in that order.
If a fire, then close all cabin vents (or as defined in the POH) and make all turns away from the fire, e.g. if the fire is coming from the left side of the cowling, then make all turns to the right. In either case of fire or mechanical failure you should then start running the shut down drills immediately.
Carb Heat
OFF Fuel Pump
OFF Fuel Selector
OFF Mags
OFF Unnecessary Electrics
OFF Squawk
7700 Passenger Brief (crash drill)
If time / workload permits and no sign of fire or mechanical failure, then run the "What's up" drills:
Primer
LOCKED Fuel Pump
ON Change tanks (or fuel selector on Both)
Mags
ON BOTH Mixture, Exercise then
RICH (or set for smoothest running)
Throttle, Exercise then
FULL (or set for smoothest running)
Carb Heat, Exercise then
ON (or set for smoothest running)
If prop stopped, Starter
CRANK
But importantly,
If at or below about 1,500 feet, or you have a high workload in maintaining safe control of the aircraft, or the "what's up" drills have failed to restart the engine, then proceed directly to the shut down drills as above.
In all cases, plan your descent to land into wind using the techniques you have been instructed in. (e.g. constant reference point technique etc)
When time permits, TX "Mayday" on current ATC frequency or 121.5
Station called (or "All Stations")
MAYDAY MAYDAY MAYDAY
Who you are (e.g. N1234A)
What you are (e.g. Cessna 152)
What's up (e.g. Engine Failure with Fire)
Where you are (e.g. approximately 5 miles southwest of Massey Ranch, passing altitude 2,000 feet and descending)
Where you're going (e.g. Emergency Landing on farmland adjacent to I-95, near a mast and a small lake)
POB (e.g. 2 Persons on Board)
Request (e.g. Request Fire service and ground assistance ASAP)
After the shut down drills have been performed, then the final approach checks should be along the lines of:
Gear Down and Locked (as appropriate - and this might get done earlier according to the POH if an engine failure warrants manual deployment)
Master / Alternator
OFF (when below 500ft AGL and on a Cessna when finished with electric flaps)
Harnesses
SECURE Exit Door
OPEN (and allow to trail open.)
Passenger command
"BRACE BRACE BRACE"
Practice:
Go around by 500ft or
Touchdown (if a real emergency or conducting the approach according to normal aviation practice into an airfield.)
The point at which you kill the Master / Alternator electrics is open to some debate. I was always of the opinion (and it is no more than an opinion) that once the electric flaps are deployed and the Radio has been finished with, then the one remaining concern is your visibility to ATC while squawking 7700. But below about 500 feet AGL it is unlikely that you will be on radar anymore so this would be a good time to kill the Master. This would normally be around the base to final turn if the profile is approximating a normal glide approach.
Anyway, I hope this helps.