One of my favorite tricks I use to help me while I am creating is to create a model of the appendage I am working on. This is something I do when I am having trouble with a particular appendage, or I want to add a lot of detail to a particular appendage. A simple example of how this can be done is by using a kite base as a substitute for a bird base when working on the head of the bird. If I wanted to make a more elaborate bird head, it would not be necessary to fold the bird base in its entirety; I would only need to replicate the section that would make up the head. In this case, the kite base does exactly that.
The advantages of doing this sort of modeling are numerous. Since the majority of the paper is being used for the concerned appendages, it is easy to work with something that is much larger than you normally would with a given sized paper. In many cases, you can form your appendage from multiple corners of the paper, making it easier to try out different ideas. Folding the model is often easier than normal, as often the layers of your appendage are less restricted. This will make you more apt to try more difficult moves, such as closed sinks, and other procedures that requite layers to be inverted. Folding is also easier in many cases, as it is not always necessary to replicate all of the layers from the complete model.
The actual figuring out of how to create a model for your appendage can be an exercise in itself. Doing this has often given me a new perspective on my model. I will have to unfold large portions of my model to figure out which portions contribute to the making of the appendage I am working on. It then becomes more apparent how the layers of your model fit together.
After you have developed your appendage to satisfaction, the next step would be to try it out on the full-fledged model. Sometimes you might have to adjust the proportions of your appendage, but usually the corrective measures for these problems are trivial. I often find it exciting to finally integrate a piece of a model I had been working on into a completed work.