The stuff you find should reflect differences … in character and size. Flat and thin, flat and fat, fat and chunky, skinny and long. Big, medium, little (but not micro-scopic). The greater the variety, the more interesting the sketches will be.
You can’t have too much to choose from. You can have too few.
Lay the assortment out and look at the collection. If it’s all about one kind of thing (line for example), search around for some stuff to contrast the mix.
When you have an interesting bunch of stuff, pick out things that look strange together. Hold two of them up and position them to each other. Do they suggest some overall thing? Pick some other things and add them to the first two. Now, build an object with them. The overall object may look like what you initially wanted … or it may suggest something new. Go for it. This is sketching.
Don’t design. Sketch knowing that when done it is far from a design.
Sketches should not look labored or finished. Nor should they collapse if jiggled. Use glue, tape, string, nails, screws … whatever, to hold them up the way you want them to be seen. Spend about 1/2 hour on a sketch. It should look alive.
The sketch should be interesting in the round. It shouldn’t read from one side. As you work on a sketch, turn it around so that you don’t have a favorite position.
The sketch shouldn’t be neutral … add up to a blob (basketball). Think giraffe … not koala bear.
Don’t fall in love with one idea … and then do assorted versions of that. Try to make your sketches as different from each other as the pieces and parts are.
The sketch is not about the things (or any one particular thing) that make it up. It is about the sum of the total. (link to original text: Lenny Bacich)