OK, I've been poking around the net and found some sites with some good info from mechanics that deal with "barnyard" finds. This wouldn't really be worth the trouble for something like a $500 Honda that has sat for a few years but more along the lines of the situation I have, a car that's worth taking the time and spending a few extra hundred on before starting it.
1) Stains: Look under the car for stains on the driveway. This can reveal issues that should be addressed before trying to start the car. Don't forget to check the rear of the car because of the fuel tank and differential (if applicable).
2) Engine Bay: Look for signs of visitors. Nesting critters leave traces like seed/nut shells, straw, leafs, insulation, and urine/feces. If you see any of these start checking wires, vacuum lines, and hoses. (see my intro post). While you're at it inspect the belts for any signs of rot or memory where they wrap around the pulleys. Adjust the belt tension if needed. After sitting for a few years it's going to need a new battery so replace it and check the cables and ground. Clean terminals or replace them.
2) Coolant: Check radiator hoses and fittings for any leaks, bulges, rot, or cracks, especially at the clamps. Give the hoses a squeeze and replace any that are suspect. Check around the water pump (some have weep hole) as a leak here indicates the internal seal is bad. Check fittings and mounts on the radiator for signs of leaks or rust. Check fins on the radiator to insure it will have good air flow. Drain and replace the coolant.
3) Fuel: Check the tank for rust or signs of leaks, inspect the fuel lines for rot and don't forget about the in-line filter. Check the rubber filler hose on the fuel tank and also the electrical harness while you're there. After you followed the fuel line back to the engine bay check the vacuum line on the fuel pressure regulator for cracks or rot. You have 2 choices if there is old fuel in the tank, drain it or treat it. Fuels containing ethanol can phase separate and there are products you can use to determine this and re-emulsify the mixture. Personally, I'm draining the tank since I am replacing the pump and sending unit. Exhaust: While you're under the car check the components for rust including the hangers and clamps.
4) Holler at the old lady to bring you a beer. Since that obviously didn't work, wash your hands and get one yourself. Carefully try to avoid her glaring stare and avoid making a comment about her weight as you head back outside.
5) Brake system. After 18 months of sitting, brake fluids that contain glycol should be replaced. Drain, flush and and refill the brake system. Bleed the brakes. Check each wheel by having someone step on the brakes as you rotate each wheel. Don't forget to check the e-brake by setting it gradually as you turn the rear wheels. You should feel the increased friction until the wheels lock and you should have a smooth release. While you're there check air pressure in the tires and inspect the sidewalls and between the treads for any cracks. Check lug nuts and torque to spec.
6) Text your buddy and complain that your old lady didn't bring you a beer so you had to get it yourself and you are ready for another one. Return inside and grab a fresh beer without washing your hands. This is the manly way to protest, so long as she doesn't actually see your dirty hands. Sneak back outside before she sees the hand prints on the fridge. Text your buddy again and tell him how cool you are.
7) Oil and Lubricants: ENGINE) A car that sits has open valves on the intake and exhaust so moisture will have gotten into the crankcase. If the car was stored with a good quality oil, the amount of rust and corrosion will be minimal unless it's been siting for a decade or more. If the car has been in storage for 2 years or more, change the oil and the filter before you try and start the car. Less than 2 years – plan on changing the oil and filter after the first 30 minute drive. Because of the money invested in my engine I'm going to take this a few steps further. I am dropping the oil pan to clean it and replace the oil pump screen. I will pull the plugs and squirt a little bit of oil into the cylinders and give it 24 hours. I am also going to pull the valve covers to inspect the top end but before I reinstall the valve covers, while the plugs are out, I will crank the car to prime the oil pump and make sure oil is getting to the rocker assembly. It is recommended to pull the tappets (carefully noting their original location) before you crank the car so you don't scuff the foot or face. Once I see everything is working ok I'll use cam lube on the tappets then reinstall them, the valve covers (with new gaskets), and install new plugs. DRIVE TRAIN - SUSPENSION) I'm going to have the car towed to the guy that built the transmission and have him service it, replace the differential lube, check axle seals, wheel bearings, u-joints, grease everything with a fitting and inspect boots, shocks, etc.
8) Check lights, turn signals, hazards. That's so self explanatory it's worthy of another beer. By now your old lady is probably watching some stupid reality show about real housewives so try not to vomit as you grab a fresh beer. On a good note, ten bucks says if you glance at the TV you'll see lots of cleavage. Avoid making a comment when comparing them with your old lady's cleavage, even if your old lady's cleavage is better. You just can't win this one, no matter what you say. Since you spent too much time watching the cleavage on TV you might as well grab another beer because they one you're holding is almost gone now. Head back outside and text your buddy about how stupid reality shows are but tell him how cool you are again for checking out cleavage.
9) That's it, the car is ready to start and test drive but you've had to many beers so it has to wait. But what you can do it crank her up and call your buddy so you can tell him how cool you are because your new ride is finally running again. He will suggest you drive over so he can see it and go for a ride but don't, because DUI is BAD.
EDIT: Forgot to add that it's a good idea to clean/degrease your engine so after the initial start and test drive you can inspect gaskets and seals for any leaks.