Check out creativity books, particularly Roger van Oech exercises, to jump start your ideas when creativity seems stalled. Create lists of objects that are round, associated with a season, types of foods, etc. to develop your fluency and flexibility. Think of new products to invent to work on your originality and elaboration skills. Remember in idea generation there are no rules and no right or wrong answers. Allow ideas to germinate.
Ideas are like seeds.
They need time to germinate. Often the best ideas will come after we stop consciously thinking about the problem. After a problem has been defined and idea generation through brainstorming has taken place, set the issue aside for a day or so. Often you'll find, that in the intervening time, some new ideas have surfaced or a combination of several ideas needs to be considered. Then regroup and select the top three to four ideas to consider implementing.