Well, first you need to address what you'd like to accomplish with
this build- Do you want to attempt some new construction or finishing
techniques? Do you want to try some (new to you) recovery method?
How about staging or clustering? Or maybe just build and fly! Do you
want something BIG or smaller?
Then, you might want to consider where your interests are- science fiction,
futuristic fantasy, scale, odd-roc, performance, payload, 3FNC, kit-bashing or
cloning?
Infinite possibilities! Keep in mind, you might be able to combine some
of these design goals and ideas, but not all.
Once you've narrowed down your choices to a few items, try a quick
internet search looking for inspiration. For example, if you want to try
a sci-fi or fantasy rocket, visit some sites devoted to those themes (or use
google images- you'd be surprised what pops up for "sci-fi rocket").
Also, don't forget your library (remember that place where everyone
went to before HTML was invented)?
Finally, I've often had success (and fun), when I pull out all the spare
and scratch parts and lay them out on the floor. Then imagine how some
of the pieces fit together. Sometimes just putting the parts in a different
setting will suggest something wonderful. You might even rediscover a part
or two you'd forgotten!
HTH!
P.S. Be sure to keep use posted (including pictures) on your progress!