It's difficult when you've got deadlines, but if they're lenient I'd say take a break. The worst thing you can do is force yourself to go on and on. It's those moments when I'm in the shower or I'm getting a train that the ideas will come – it's not necessarily when I'm sat at my desk. Get out of your usual workspace. With creative block, a lot of the time we interject our inner critic. You're in your ideas process thinking "That won't work because of this, this won't work because of that". It's the complete opposite of what you want to be doing in the idea generation phase. You want to be springboarding and not saying no to your ideas. Write anything down – the second stage is to go back and refine.