Whatever ideation technic you use, there are a few good practices that you can follow to make your life easier. Here a selection of the ones I personally use.

Title and explanation

Ask participants to always add for each idea at least a title and a short explanation. The whole thing can be the length of tweet or short text message. 
This is helpful especially when you need to come back to the ideas a few days later. 
If people feel comfortable enough to add a sketch it's great, but having only a sketch for an idea will be pretty terrible when you'll come back to the ideas later.

One idea per support

If you are working with sticky notes I recommend you use one sticky note per idea. Don't list several ideas on one sticky note.
This is helpful when you'll arrive at the prioritization phase as you'll have to move ideas to different places. If there are multiple ideas on the same support you'll lose a shitload of time.

Write in capital letters if done by hand

Ask people to always write titles and descriptions in capital letters.
This is helpful because some people have a terrible handwriting. By writing in capital letters there are more chances you'll be able to read what people write. I usually remind this rule a few times during the ideation sessions as it often gets forgotten when people get in the flow.