The biggest threat is stale gasoline. I once left a truck in storage for a year and the old gas turned partly to varnish and stuck all the valves. It was very expensive to free them.
Drain your gas from the tank and start with fresh stuff. Add one oz. of automatic transmission fluid (ATF) for every gallon of gasoline. Use gas stabilizer in the future before long-term storage.
The next biggest threat is stuck piston rings. Moisture rusts metal parts. I had a marine engine destroyed by this problem after leaving it in storage during the winter. The engine ran for a few weeks, but the stuck rings scored the cylinder walls and destroyed the engine.
You can free any stuck piston rings by removing the spark plugs, pouring 2-3 ounces of ATF into each cylinder, and cranking the engine a few seconds with the spark plugs removed. Allow the vehicle to sit a minimum of two days before attempting to start it. Warming the engine without starting will help greatly, such as by sunlight, space heater, etc. Before starting, drain & refill the crankcase with fresh motor oil, but substitute twenty percent with ATF. Once the car is up and running, drive the car at highway speed for a minimum 200 miles (max. 500) and change the oil again, substituting five percent with ATF.
The third major problem is corrosion in the cooling system. Another car I once stored for two years had major scale buildup in the radiator. Solution: Flush the radiator with a radiator flush solution before changing the coolant. Typically these solutions contain citric acid, which is highly effective and safe. Another trick is to drain & fill the cooling system with water mixed dish washing liquid you find in the supermarket, then refill with fresh coolant.