Old Hondas never die, they just wait.
I have not heard such a true statement before!
I agree with most of what has been said here, but have my own approach to it. I will just assume that it needs a few things and make sure to do it meticulously and correctly the first time. Bodywork and seat aside (those things do not cause the bike to work or not, just appearance is all, and that is not the major concern at the time).
I would definately put some oil in the cylinders through the spark plugs and let it sit for at least a day, then add just another teaspoon more. Then, I could remove the alternator cover and use a rotor bolt on the wrench to turn the engine - this way you an do it SLOWLY and with control.
Oh, back up one step - before I did this, I would a.) order carb gasket sets from yamahaoftroy.com (yes, I realize it is a Honda and this place is the largest national Honda parts dealer, they just also have yamahas and chose that name I suppose) - be sure to order the same number of sets as you have carbs. Then take the carbs completely apart (getting a clymer's or, if you are lucky, an OEM manual - sometimes, depending on the bike, you can find these online, will help). Also, you will want to get a bucket of carb cleaner (I used Berryman's for mine - Autozone has it, and it worked great!). Discard all the old o rings and place the carb body, jets, needle, etc. into the cleaner to soak. The directions say 15-30 minutes. Huh uh - more like 3 days (it will not hurt it, trust me, I just did it). I would also soak the floats in here for about 1 day. Pull them out - shake them - if there is liquid in them, they are shot - get new sets (again, happened to me). Also, do NOT put the needle piston with the diaphragm in the cleaner, it will kill the diphragm. Carefully inspect this diaphragm for any tears, dryrot, holes, etc. If you have any of these, they need to be replaced. I usually clean this with mild soap and water and then clean them off with the "natural" armor all protectant -but be sure to wipe it all back off - this will increase the life of it.
Once the carbs come out - be sure to scrub the parts with a toothbrush and I used canned carb cleaner to shoot through all the little holes in the carb body and the jets - then follow this up with compressed air. Put these all back together, and your carbs should be fine.
Check the condition of the tank - I am willing to bet that there is rust in it (possibly varnish as well). You can coat the tank, but if I were you, to save on money at this point, I would simply clean it as best as I could and then use in-line fuel filters to start with, you can coat the tank later if you want. That reminds me, I would take the fuel valve apart and clean it and put it back together too. (Get the point, lots o cleaning! But well worth it, I say).
New plugs are a given...
Now back to the engine - with the oil settled in, slowly turn the engine around a few times - hopefully you can feel the compression building up and releasing as you turn it. I would also take off the tappet covers and watch the rocker arms and valves move. I would also take the points cover off and check the movement on those as well. If you cannot turn it - then, while it is not horrible news, it means your engine is seized which requires more work, however, I am thinking that this would be unlikely, unless it siezed before it was left sitting.
You will probably need to adjust the cam chain tension, which on a honda is probably very easy to do (cannot really give details until I know what bike it is).
Next, I would check the points, be sure that they are opening and closing as they should and are in good condition. If they are not, you can try to clean them a bit, or simply replace them. I would guess that they are probably good enough though.
As I have just found out, the timing is pretty darn easy to fix so long as you have the right tools - I made a timing bulb out of an old lawnmower light, some 12 guage wire and two alligator clips - works like a charm. the index marks on the rotor makes this job pretty simple.
Now, to avoid more work and money at this point, I would change the oil and then try to start her up. It will probably take a few times, but hek with Honda's it may take only two time if everything is done correctly. See how that works.
There are a couple other things to tweak, but I wouldn't think it would be necessary at this point (i.e., the gap between the rocker arms and the valve stem, etc.)
I know it sounds like a lot, and it will take a bit of time and patience, but it will be all worth it when you hear it fire up the first time.
It really isn't too much once you get into it.
Oh, I almost forgot, this is just to get it running - you will need to pay attention to other things before you actually ride it. Adjust cables, fix brakes, lube cables (or replace if needed), tires, etc. Oh, and wash it, there is dissenting opinion on this, but I say a bike that has been sitting so long runs much better after it has been cleaned! Same as people!
Good luck, it can be done, and let's see some pictures as soon as you get it!