Brainstorming (and its variations) is probably the most well known and widely employed method for ideas generation.
Here are a couple of slightly different approaches.
Consider the problem; ‘draw a dragon’
Then specify the parameters; Colour, Wings, Size, Defence.
Next list some variations for each parameter;
Now make random combinations by choosing one variation for each parameter;
A blue dragon with no wings which fits in your pocket and smells bad.
Now all you have to do is choose the best combination!
Try it yourself, do a morphological analysis for the problem “what shall we have for dinner tonight”.