And the best way to have a lot of ideas is to give your inner critic time off when you are generating ideas.
Come up with as many as possible, write the all down (yes, even the bad ones), and put them aside.
Have a separate session for evaluating which ones you want to develop further.
(You'll find lots of tips about getting into a creative mindset, methods for generating ideas, and turning your ideas into action in my book, Creativity Now, publishing by Pearson and available from Amazon or your other favorite bookseller.)