Hard as it is to say how to design, it is easy to say how not to design Apparently, what constitutes a successful way of working depends very much on the specific design problem, the situation and the character of the designer, but failure and incompetence are universal.

OK, how do you fail as a designer? Well.

Always cling to your first idea.

Jump into the details immediately.

Solve one aspect of the problem first.

Ignore a stakeholder, preferably a vital one.

First design the form, then sort out how the thing should work

Promise too much to the client, really inflate his expectations.

Don't listen to your client, lie to him if necessary.

Be inflexible in your ideas and approach.

Try to surprise your client with a completed design.

Ignore any tests that say the design might be below par.

Wait for inspiration.

Stay 'fresh' by not gathering information.

Do not plan (because that takes too much time).

And so on.

This is a good but uncomfortable exercise in self-reflection. We are all sinners, some of the time.