There's a variety of material for planners out there, some old, some new.
Choose which one suits you, depending on your level and your learning style.
Barry Elkington has produced superb, highly readable and nicely illustrated advice for those planning each of the colour-coded courses:
Thanks to Barry Elkington.
Purple Pen is the club's course planning software of choice and a really useful tool. It's also free to download.
Paul Taunton of North Glos OC has produced a lively and instructive document that was originally used as a presentation but still reads very well (Nov 2018)