So some brief advice from spending about 5 years as a visualization engineer/designer/data scientist:

1. Get an intuitive understanding of the data

2. (via Alberto Cairo) Aim to allow the user to correlate, organize and compare this data

3. Come up with a few visual means to do no. 2, and get feedback and iterate.

4. Go to the catalogs and see what work has already been done on your version of 3, and then implement.

It is amazing how many "original" charts I have created which have already been named and studied from a perceptual science point of view. But it is still important to come to a clear understanding from your own point of view of how the data fits that representation.