Check for fuel. Fresh will be better than stale (that"s if there is any in it). Check valve is in "on" position. Check any fuel filter in the line.
Check for spark - if it is gas
Check for sticking valves (not likely the immediate problem).
Check for compression - rings may be stuck and bores dry after that long.
Check that nothing has unfortunately broken or stuck since it last ran (eg throttle, inlet manifold [or gasket]).
One last thing check the oil and make sure it has some lube circulating BEFORE starting it up - running on dry bearings will not be good for the engine!
Check ignition cut-off if it has one.
All normal everyday things like these should help you locate and perhaps fix the reason for non-starting.