Finding your own voice is important. Though it may seem counter-intuitive, using models can be a good way to do this. I don't mean models in the sense of three-dimensional representations of physical objects, of course, but rather "models" in the sense that we try to copy or imitate some other work.
We need to keep in mind, of course, the intention to create something that represents what we believe not what our model believes.
In writing a dissertation, models are tremendously useful; they provide clear insight into what gets accepted by your professor. It's also something that many don't think of doing in academia (many do, but many don't). You can model an academic work without plagiarizing or imitating--all you have to do is change some of the basic presumptions or questions and then try to copy the structure of the model without copying its reasoning. If you need a theoretical framework, again, another dissertation (or other academic work) can provide a good source.
When you're honestly trying to adapt someone else's model to fit your own interests and intentions, the project will naturally develop in a manner distinct from your model--plagiarizing is not a danger (especially if you're giving credit where credit is due).
When writing fiction models may be trickier--but then again maybe not. The key is to make sure that you're adapting your model, not just adopting it and putting on new makeup. Some of the greatest works of art are copies and rewrites--Shakespeare continually re-used old themes and old sources.
I'm thinking about models because I've been writing in this blog more recently, and I wonder about the blog form. So far what I've written has largely been a string of short essays, each pretty much coherent in its whole. But blogs--the blog form--is somewhat more fluid. Indeed, one aspect of blogs that is very appealing to many is the inclusion of information that is not the author's own, but rather shows the author's connectedness to other good information sources. I don't link much primarily because I don't surf much. I don't really know what resources are out there on the Internet; I know in an abstract sense that there must be loads of information dedicated to writing technique and writing practice, but that's not an area I'm extremely familiar with--I tend more to think things through on my own than to do research to see what others are doing. But the blog model is a good one to use to prompt me to expand my habits and practices. Not to mention, including other sources would give me more to talk about.
One good thing about making a choice to use models is that it helps to remove the stigma of being imitative. There is, at least in the US, stigma attached to the idea of imitation. But, as Shakespeare helps us remember, imitation does not imply lack of creativity. If we are using and changing the models, we are engaged in the creative process.