My sketching tools:
Moleskine sketchbooks. These are the large (5.25" x 8.25"), plain paper, matched color Volant set in green. They are thin and lightweight to carry everywhere. I always have both -- the lighter for drawing ideas or inspirations I run across and the darker for writing notes about projects or classes.
Amy Butler "SunBlooms" Notebook. I use this for my more introspective journaling which I go back and add to periodically. Lists of favorite artists and why I love their work. Lists of words I want applied to my work and words I want to avoid. Lists of themes I want to incorporate into my work. And so on. Some day I want to replace this with a journal I've decorated myself.
Zig Millenium Markers. I carry a set of five sizes of nice black, waterproof markers, from size 005 to 08. I think these are being discontinued so I'll need to switch to others from my copious stash.
Derwent Watercolor Pencils. I have watercolor pencils everywhere, every brand. I love them all. I carry them in a lightweight plastic pencil box.
Niji Water Brush. This is the secret to toting watercolor pencils. Just rough in color with the pencil, then blend and spread with the brush. I don't use watercolor paper Moleskines, which have heavier paper, so I just draw on one side of the thin paper and try not to use too much water. Next to the water brush are a set of metallic pencils that I picked up in Paris.
Of course, I carry standard pens and pencils, an X-acto knife and a glue pen. To keep all nice and collected, I found this great polyester toiletry bag by Ann Millie, which tucks into my larger tote bag.
My rule for sketching is everything in ink; I don't draw in pencil. Mistakes happen. Learning to incorporate them into the work to continue, rather than starting over, is a invaluable skill. That's not to say there are no goofs in my book, but 90%+ of the drawings are completed satisfactorily. I don't do fancy work, just quick sketches to get the idea down. And I often do sets of drawings, like the glass and silver pendants above, which were all on a page together, drawn on the train from London to Paris. There were more sketches along these lines on another page. Working in series is the best way to quickly improve the designs. I'm not very attached to any one of them, but trust that among the lot I will find something I like. I did like this idea, and the finished work looks pretty similar to what I visualized. I say "if I can draw it, I can make it."