Hello hdat ;)
Great question! I congratulate you for your goal of becoming an intermediate certified developer.
The most effective way to study for an exam is to be involved in a practical project either at work or maybe you can find one by asking a friend in your network. Second to that would be to go through all the learning paths that are being pointed to from the mendix academy for the exam.
These are the necessary learning paths for the intermediate exam:
Hello hdat,
In addition to what Marcian-Petrut Bondoc-Popescu shared, I'd also like to add something.
I got my certification last year. To prepare, I looked up each item of the 'Modules' in the Mendix Documentation and studied them thoroughly. It really helped me understand Mendix better and get ready for the exam.