Some great responses here. I'd like to highlight something Brad mentioned. Once an engine's been tuned (and run a gallon or two of fuel through it), you shouldn't ever have to adjust it, so no worries about flying alone. If the engine starts giving you trouble after it's been tuned and broken in, it's probably not the engine.

A thin trail of smoke in the air is a pretty sight with a new engine (or even not-so-new). That indicates a nice, cool rich mixture.

The only other thing I would add is that the usual tuning methods (as descibed by Brad) work fine on an engine where the low-speed adjustment is somewhere close to where it should be. That's almost always the case when you buy from the manufacturer or distributor. If you buy a used engine, you never know. If the low-speed setting is off the engine will be very reluctant to start, no matter what you do with the high-speed needle. On an air-bleed type carb, a half-covered bleed hole is somewhere close. On an all-needle carb, it's hard to tell. Best advice is, don't mess with the low-speed needle unless you have to, and then make your adjustments 1/8 turn at a time. 1/8 turn makes a big difference.