I've tried many different things like Evernote, Trello, enormous ToDo apps and other stuff. I guess everything depends on personal taste, but I've finally discovered the more abilities the application has, the more time I spend on it. All of them has finally become useless but beautiful apps.
However, I do use Trello, but only for my commissioned works, since it's a good system for my customers to track the process. But I didn't find it useful for my comics
Then I've tried to use some paper planners. That worked better for me, but I got carried away with "bullet journals'. They are so beautiful and inspire me so much. But again I've lost more time on filling in the planner, so it finally became a beautiful and useless thing.
Currently I just have a paper notebook with a nice cover. It is not too big, so I can always take it with me wherever I go. Each month I draw a table and write a ToDo list. If I have any ideas, I write them right there. This doesn't take much time, but seems to be useful and clear. At the same time filling in the paper planner helps me to have rest and concentrate.
Oh, and I guess using color codes is a good thing too
As for mobile apps, I like Google Tasks. It is a simple application, but it integrates well with Google Tables (I use it to collect my statistics on subscribers and personal achievements) and Google Docs (I use it for all my plot scripts). All these apps are simple, useful and available both on my laptop and mobile phone, which is very important because I am the person, who may wake up at 4 a.m. with desperate need to write down new ideas
I would really recommend to try different ways and find the one that suits best for you)
