Sketch books are for everyone - children included. Good for ideas, poetry, notes, doodles or whatever. Different sizes: small ones fit in jacket pockets or bags, larger ones for use in the studio and ‘official’ work on a project; brainstorming, notes on different techniques, inspiring quotes and other artists. Serviettes, programmes and newspaper can also be used when out and about and feeling inspired. Mentors encourage daily sketching to hone drawing skills.
Sketchbooks can be used in a variety of ways. Enjoy regular sketching times with friends in gardens, cities, museums etc; these sketches are a great resource. My sketch of a stuffed zebra head in the Brighton Booth museum morphed via a Matisse inspired paper cut into my logo some years later .
Random holiday sketches recapture forgotten memories, or give opportunities to experiment with new equipment e.g. a new Pentel brush pen. Feel good equipment: that brush pen, not cheap - get one for the artist you love; I love my small paintbox and travelling paintbrush where the precious brush head is protected by a cover, brass is nice .
I can often start with an idea but not know how the eventual piece will end up. I find the Brushes redux App (made famous by David Hockney) on the iPad another useful resource.