Hmm.. sounds like fun, post a few pics so we can see what you've scored.
First off, I'd check all the bolts screw etc and make sure it's tight.
Next I'd probably pull the plug (check the colour of it to see if the engine's been used with it, and if it's been running rich or lean) and walk it back and forth with the clutch engaged (plug out, fuel off) and have a listen to it. It should make a nice little whut-whut-whut as the cylander cycles, and by putting a thumb or finger in the plug hole you'll be able to confirm compression. If the motor won't turn or doesn't seem to be getting good compression you may have to go a little farther with a rebuild by checking rings, gaskets etc. With the plug in the boot, lay it on the cylander head as you're walking it and watch for any hint of spark as well, although a voltmeter can be used just as easily instead. If it has no spark, it's usually one of only a couple of things, CDI or magneto, or possibly poor wiring.
After that, eyeball the drive chain and sprocket, make sure they're both good. Check the fuel line, cables etc for cracking, hardening and so on.
The only fluid to wory about it the fuel.. not knowing the engine's history I'd probably err on the side of caution and go with a mix a bit closer to starter mix for the first tank, somewhere around 20:1.
I'm sure there's a lot of other things to check for, that's just off the top of my head halfway through my first coffee of the day.