tune the engine after it has warmed.
once the engine has been set, you shouldn't have to mess with the setting
that much. tweaking with the needles all the time is just asking for trouble.

you must compensate for altitude. richer on the ground .....
hold the nose up and tune, then back out the needle around 1/4 trun
a buddie holding the TX is very helpful..better yet, let him hold the plane nose up

i personnally always stand behind the prop or the plane.
use a steak or a device to hold the plane back
NEVER reach over the prop..common sense would also tell you not to
tune the LSN while the prop is spinning...

you must also compensate for weather conditions.
denser cold air require more fuel or a richer setting...

a smoke trail is healthy..but don't be fooled, a too lean or too hot engine
will also smoke.

you can also try using a different temperature glow plug to better suit your needs.

it takes time to get use to engine sounds or the sounds of differnent props.
lower pitch is rich
higher pitch is lean.

seal the engine... backplate, carb, ect.
i sometimes jb weld the carb to the engine on certain engine brands.

loose mounting screws will also make the engine run funnie.
makesure everything is nice and tight.
a balanced prop will help too.