There is some good advice here, but it's vague advice. I think some more specifics on your rod wt/line choice/leader type and length/ fly wt would yield some more specific, good advice on your trouble. I only chime in because, I really received no formal education on casting, and it is taking me forever to learn the hard way. I have tended to find my own solutions, but slowly, through "A-HA" moments. I am a horrible caster, considering how many flies I've thrown. Being not a part of a local fly fishing community, and most of the people I know gear fish or don't fish. I just do my own thing. Even though my fly buddies that introduced me to this are split-shot, big pooftie-yarn-dicator types or straight dry fly guys, I wandered away toward big ugly streamers, cuz it was fun to me. What I do know is that the article Rip Tide posted sounds a lot like what I spent years trying to figure out alone, mostly cuz no-one I fished with was doing it. I just read that article, but I think I'm gonna read it three more times. It's making sense. It sounds like what I've discovered slowly by accident, wish I woulda been reading about fly casting a long time ago, no one told me. I didn't learn basketball from a book or magazine, but I'm pretty damn good at it. Just realizing, fly fishing is a different kinda sport.
Big uglies cast quite different. It's not the rod, as you wondered and were asking, as I have several, distinctly different rod actions in my quiver, and I have been forced to learn to throw streamers on each. It's my tempo that needs to adjust, and the length of line I choose to let out the tip top at the starting point that changes with each rod/line/leader/fly combo. And each combo takes me a while to figure out as I change setups. But now, reading that midcurrent article. I think thats an absolute, spot on, place to start. Then start adjusting your tempo to find the balance. And hey, give some more info here, you might have a rigging issue you don't realize. Someone might notice, and likely, would be happy to help I'm sure. In the mean time, hell yes, we all catch a few shots in the back of the head, cause its an awkward casting style at first. Throw some more of the 411 on your rig.
Randy and Chrome both have good advise, the lowdown....Open up your loop quite a bit and dont make a bunch of false casts.....When your using heavy streamers you want to pick up alot of line and shoot from there. One more thing thats pretty important, dont be scared...If it really worries you turn your cast off to the side just a little.....
Damato, another good point, that I will ignorantly agree with as a a newbie. False casts, with awkward heavy setups, are more harm then good in the early stages. I tried it, as a dork, that didn't know they were different animals... can be done, and I've learned to do it, but, an advanced skill for better guys than me, to be sure. Honestly, remembering back to when I couldn't toss a streamer, my first cheat was to water load any cast I could, even if it was a three or four point cast, it will get you in the zone before an ugly, weight affected, overhead style, cast that wasn't meant to throw that rig. Saves a lot of fishing time from wondering what went wrong. Fishing sooner = fishing more. Those wide ranging water-loads developed into an understanding of tempo, that were evolved into my own streamer casting style for each of my rods. A-La the eliptical cast Rip referred to. I just got there the hard way.
Absolutely don't false cast this setup till you figure out what it really takes to move it out to the target.
Mojo, I'm curious about this, cause, I'm still trying to figure it out myself. Is what you are saying .. to move your arm further back to 2 o'clock so the rod bends less? Just unrolling line by its own accord, instead of stopping short and letting the rod load? Confused but curious.