It's always worth getting someone to proofread your submissions. All co-authors should anyway, and those less involved with that aspect of the work can be best qualified to judge the clarity of your exaplanations (they can also be most liekly to skim over that section). Otherwise, you have peers, help each other. The best style partly depends where your figure is going.
In a journal paper, styles vary between journals, even from the same publisher. Some like dense figures with long captions, or at least, these become the norm when page limits are tight. Other journals prefer more spacious figures, fewer insets, and simpler captions. The correlation between cpation and figure styles is only meant to be indicative; I'm sure you could find examples of simple figures and very full captions. Some journals prefer the legend to be given in the form of text in the caption.
In a thesis you'll normally have a list of figures, with short captions in it. These short captions should give enough information for the reader to find a figure ("There was a figure relating bandgap and lattice spacing, now which figure was it?") while including a subset of the information in a full caption. Thus the full caption will end up reasonably descriptive.
There are a few other, competing, factors:
- Help your reader. This is a point I often make, but here could be interpreted as:
- Don't waste space and the reader's attention stating the obvious...
- ... but add clarity.
- If a figure really works only in colour (and these should be rare), provide enough information so the reader knows this, and doesn't juyst hink your figure is rubbish.
- Consider a reader who may not see too well -- give them the information in text to decide whether to print a large copy. (This is an example, but helping this hypothetical reader may help all your readers).
- Help the reviewer. This overalps with helping the reader, but a reviewer will be looking for different things. By all means say "for a full description of the samples, see main text", but rather than just "Sample A (red squares), Sample B (black circles)" give them a gentle reminder of which sample is which (this of course is easy if it's a treated and a control population).