Having attended three CR courses, own most of his books and videos, I have compiled a list of bullet points that Charles constantly emphasizes. Here they are in no particular order.
1. First Squint - less is more -is image dark against light - light against dark?
2. Vary finish. Adjust value and colour intensity throughout painting.
3. When short of time begin with darks.
4. Shadow and cast shadow shapes are painting foundation, close in tonal value, but colours varied and mixed on paper.
5. Accurate shapes.
6. Patience and timing! Don't hurry!
7. Basics. Shapes, good tonal value, first try and lose boundaries when two similar tonal values meet.
8. Magic Triangle (1). Three dominant colours or local value shapes form a triangle within painting, two near two of the boundaries and third nearer third boundary or closer to edge.
9. Mix on paper. Less mixing cleaner and clearer colours.
10. Magic Triangle (2). Find two or three elements that you really want to paint. Paint as carefully as possible then omit or simplify rest.
11. Design your page. using areas of explicit detail.
12. Place People first.
13. Edge Control. Soften edges when painting. Squint if easy to see make it hard, if difficult soften.
14. Paint what's offbeat.
15. Background should support subject but not dominate! Is something in background essential or potentially dangerous? If so leave out!
16. Buildings. Darker tones and detailed towards top. Simplify and lighten middle section, darker tones and more detail at base.
17. Creating success. A. Shapes, local value and edges. B. Colour.
18. When outdoors always paint from dark to light.
19. Buildings. NEVER paint your minds conception of a building. Paint a collection of beautiful colour and shapes, that suggest a building.
20. Loosening up is a state of the mind!
21. Clean palette regularly when painting.
I've just added points 20 and 21 (20 -09 -10). I should have said earlier that while I would like to say I follow all the above religiously that isn't always the case. One gets carried away - at least I do - and sometimes (often?) plunge in where others fear to tread. There is a dilemma with watercolour that centres around the spontaneous nature of it. Charles and others talk about `happy' accidents (and unhappy ones) and to adopt an over deliberate approach can mitigate against the wonderful possibilities of this medium. Many will disagree, especially those who go in for super realism. Each to his own I say. One of the points above says don't hurry but take your time. In the two artists I mostly lean to, Charles Reid and Judi Whitton, they both take regular breaks when painting.
I should emphasize that the above is the Charles Reid way. Other artists may well differ and offer completely opposite `rules'. When I read my first CR book, the 2001 flower painting one, I found it difficult to assimilate the quite different approach he advocated. I put it to one side but found myself returning and gradually becoming interested and then a convert. I should say I am not a sycophantic follower, some of whom you meet on his courses. I don't rave about everything Charles does, being especially interested in his portrait, figure, and still life work, the latter combining flowers and other objects. There is good stuff in the other subjects he paints but those are my priorities.
I mentioned different approaches. This is something the would-be artist should beware. Different artists say different things and some of it is very contradictory. It is easy to become confused and this - to me - is the problem. Don't take what anyone says as gospel - they aren't always right. This is particularly so regarding things like paint choices. I may post something more on these lines at a future date with examples to prove my point. Regarding the above though I feel much of what Charles says can be usefully applied, regardless of whatever style you choose.