Honestly it's all just about making sure to write ideas / concepts down; I usually have a couple sources I can go to to reference [pinterest + toyhouse, usually]. Whenever I have ideas I usually try to name 'em and draw 'em ASAP, so it's easier to document. And ofc ideas will ebb and flow, and sometimes I do end up forgetting, but there's no reason it can't come back to me later! I'm just having fun. Having a writing partner to help me remember is a bonus too.