The 10 plus 10 ideation technique can be used to generate a large number of ideas in a short amount of time. It involves splitting participants into smaller groups and asking them to generate 10 ideas each within a set time limit. After the first round, the groups swap their ideas with another group and then build on each other's ideas to generate another 10 ideas.

Here's how to run a 10 plus 10 ideation session:

• Define the challenge. Begin by defining the challenge or problem you want to address through service design ideation. For instance, you might want to improve the user experience of a mobile banking app.
• Divide participants into smaller groups. Divide participants into smaller groups of around 3-5 people. Make sure each group has a mix of skills and perspectives to encourage diverse ideas.
• Set a time limit. Set a time limit of 5-10 minutes and ask each group to come up with 10 ideas relevant to your challenge.
• Swap ideas with another group. Once the time is up, ask each group to swap their ideas with another group. Each group should read and analyze the ideas they received and then build on them to come up with another 10 ideas.
• Collect and share ideas. Use a whiteboard or other visual aid to organize and categorize the ideas.
• Discuss and prioritize ideas. Have a group discussion about the ideas generated, and identify the ones that have the most potential or are the most feasible to implement. Prioritize the ideas and create an action plan for further development and implementation.