I think uniqueness just matters more to me than to you, Bratty. That's just fine.
Mapping is a process with many different sides. There's the technical side which will cause quite some problems first but you'll get over that if you invest some time learning things and experimenting (and here I agree with Bratty that the maps of others are useable - as examples and such).
Then there's the design part, roughly divided into a visual part and a gameplay part. They're related somewhat but there's still quite a difference between them. I believe this part requires the most insight or talent. You will need insight in how the game plays, in what makes maps fun to play and what not. Again, others have written about this and playtesting helps with experimenting here. The visual part is developing a feeling for what fits together, what looks good, where detail is best spent, and so on.
There's still more to it than these things. Besides the technical side there's the art side as well. Creating textures, models and so on can be considered as part of the level-design process.
Conclusion I know this is sort of a chaotic rant about my view on mapping, but what I'm trying to say is that it's best to experiment with the technical side a bit before attempting a map you intend to release. Creating a map goes much better once you're a little familiar with the tools and all.
As for what I'm mapping for, mainly HL2DM at the moment.