Ultimately, the way to get good at creating anything in any program comes down to simply using the program a lot, experimenting, and learning from practice what to do in the program to create what you see in your mind. (How to imagine good designs is even less clear-cut. :p)
Lighting and design are fairly program-independent. You'd do well to learn more about those, and to study images that you've seen that you like, regardless of what program you use.
What's unique (not in a good way :p) to Bryce is that you're restricted to primitive shapes, plus a few other odd shapes that come with the program (click the triangle next to "create" and go to the Imported Objects section), terrains, symmetrical lattices (terrains mirrored about their base), and metaballs (explained later). These are your building blocks, and they're quite limited; in other programs that allow real modeling, you can create whatever shape objects you want.
Of course, what you have to learn to do is create the shapes you want out of these basic shapes - and to do that, you have to use boolean operations of these shapes. It's not as complicated as it may appear at first; it's based on groupings of objects whose modes can be set to neutral, positive, negative, and intersect. Neutral objects will not interact with other boolean objects. Positive objects appear as normal (solid), but will interact with other boolean objects. Negative objects are invisible, except that they carve away any overlap between them and another (positive) object. Intersect objects will only allow the overlap between them and another (positive) object to render.
Thankfully, you're not even limited to that. You can create a strange shape using booleans, then group them all and set the GROUP to another boolean type; for example, you could intersect two spheres to make a magnifying-glass-lens shape, then take the sharp edge of that group and use it to cut into a positive cube.
It can get complex quickly, but as you gain familiarity with how it works, you'll be able to start making groups where you can barely tell how they were constructed, if you want to. This familiarity and ability to construct boolean groups is the key to making interesting shapes in Bryce.
I forgot to mention; of course, you can move, rotate, and scale primitives and groups and anything else, arranging them to make interesting shapes, too.
Terrains can be made to make interesting shapes, and you can sculpt objects in Photoshop by making custom greyscale height maps, once you understand how those work. Symmetrical lattices also work, and are mirrored around the base. Various tutorials you can find on the internet would explain terrain object creation better than I can.
Metaballs are spheres that act somewhat like drops of water; when they get close to one another, they start glomming together, and when they overlap, they get bigger. Undocumented feature: shift-clicking on the "create metaball" icon will create a negative metaball, which repels the surface instead of attracting it. The ship in my pic (url="http://"http://homepage.mac.com/weepul/crashlanding.jpg")here(/url) is almost completely made of metaballs.
Other tips: learn how the texturing system works. It's complicated; I learned it through experimentation and reading tutorials online. It cannot be explained very easily without diagrams and showing examples of what does what - luckily, other people have created tutorials on it which do, and of course, you can experiment to learn how things work.
Volumetrics are good for special effects. They render slowly. Best way to learn is through experimentation.
(url="http://"http://homepage.mac.com/weepul/brycefighterviews.jpg")Here(/url)'s a ships I made in Bryce...it's not particularly detailed, but you can see how booleans (the front) and metaballs (the smooth rear) can be used to create more complex forms. (url="http://"http://homepage.mac.com/weepul/brycefighter.jpg")Here(/url)'s a scene using the previous ship, plus one made from two symmetrical lattices, and lots of volumetrics for special effects. (Ignore the blurring, that was Photoshop, and ended up actually not looking that great. :p)
Mind you, those were more recent creations of mine, after some years of using the program. However, for most of my shipmaking I preferred to use other programs, so I wasn't working as hard at learning Bryce as I was other programs (and my ships that I've made with it have not been my best). The more effort you put in, the better your work will be for the skill level at which you are, and the faster your skill will improve, but it will take a lot of time and dedication.
I hope that basic introduction helps...again, for more specific help, search for tutorials online. There are a huge number of Bryce-using people on the web, and a few large communities. Resources are out there, but I also can't stress enough how important it is to fiddle with the program yourself, and learn through experience. Good luck! 
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(url="http://"http://evula.org/aftermath/")Aftermath(/url). You know you want it.
(This message has been edited by Weepul 884 (edited 07-13-2004).)
