The biggest challenge when preparing eggplant is excess moisture. When grilled this isn't a problem as the grill will evaporate the excess, this won't happen in a hot pan. The eggplant will steam in its own juices and you'll get a mushy texture and bland flavor.
Salting is the recommended techniques for drawing out excess moisture. Use larger crystal kosher salt which can be wiped away when it has done its job; the finer table salt will dissolve into the eggplant and then needs to be flushed out. It is best to place the salted eggplant on a baking sheet covered in paper towels which will wick the moisture away from the eggplant.
If you are sauteeing, diced pieces are best so the increased surface area will brown and absorb more of the flavorings. Thicker slices are best for grilling so they won't fall apart about 3/4-inch slices are best. If you are stir-frying you probably can skip the salting step as the sauces used often contain plenty of salt and the liquid isn't as much of a problem.