Many tires have colored dots on the sidewall which indicate mounting location. Depending on manufacturer the colored dot either lines up with the valve, or 180* from the valve, or indicates a 'high spot' on the tire. Contact the tire manufacturer to find out the dot 'coding'. I have yet to find a tire shop that knows this without me telling them how to fit the tires. They will usually just fit them any old way they want. On directional tires, where the dot ends up on the inside of the rim, have them chalk mark the opposite side of the tire to ensure correct fitment.
For Falken Tires (which I use exclusively):
The yellow dot is the lightest spot and it is suggested to mount this above the valve stem.
The red dot is the high point, recommended to be mounted at the low point of the rim if so marked or, preferably, per actual measurement.
Per a product engineer at Falken Tire, these marks are just "starting" points for the tire installer to effectively mount your tires. With some of the new balancing equipment out there, the machine can do a more accurate job matching and balancing then simply relying on these dots alone.
Otherwise my $$ are on ball joints.
Tim