All the points made so far are valid, but the most obvious one for me would be what is the casting Ratio of your Rod? The casting, action and recovery of the rod are all designed around specific weight ranges, using lures which weight doesnt fit into the range will cause you problems with casting or even damage it if too heavy. Generally, I find that using lures between the mid to top end of the casting ratio give you the best casts and rely less on technique. Whereas using the lighter or bottom end technique really comes into play. Technique is always important of course. Often i find that the more gentle and controlled casts provide far better results than trying to belt it out.
I also find that Lures with internal weight shift system via ball bearings cast better too.
The other point i would make would be wind speed and direction, I find using plugs upto 25g wind speeds of 10mph+ start to give me a problem if they are blowing across or from any direction towards me. Obviously when its blowing in your casting direction it carry's the Lure further!