First I take a look at any existing assets; strategy, script, brief, footage, audio to get my bearings. (If the client needs help developing a strategy and script-I can help too but it's prior to animation.) Then I being data-mining and storyboarding. Finding visual references to explore specific creative directions to inspire achievement of interesting refined details. Novelty is an important part of attraction attention and interest. Desire and action depend on the product and script.
The storyboard is where ideas specific to the project begin to take shape. It's where we rough out how any creative techniques from our visual research would integrate. (My selection criteria for those techniques is new things I can try that are achievable, engaging and appropriate.) Then we discuss, refine and approve the storyboard. The script should be locked at this point as well.
The intermediate step between storyboards and animation is what some call a ‘leica reel.’ It’s where I cut-in rough elements like storyboard frames and in-progress animation with any VO or footage. This helps us see timing for each shot as we iterate forward. Sometimes the storyboards start very loose and become tigher as the process continues. It's fun to see the project slowly take shape when each update is made.
If we have a script but it hasn’t been recorded or shot yet I often record a rough read-through to see how timing works. This can reveal flow problems we didn't anticipate and give us time to address them as required.
Some clients feel it’s jarring to see rough placeholder and polished elements mixed together, but it’s a process to get to the final. So managing expectations around any showing of these steps to those who are not creatives is important. Though we can always work on it internally until we feel it’s polished enough to show. It's a process Pixar uses to great effect.
Sound: When I’m directing I have sourced the VO & music, I have a composer I work with and can find existing tracks if needed. I’ve negotiated directly with the artist and manager before also. Mixing for Web, TV, Cinema all have different technical criteria, so the composer can manage these outputs as needed. If I'm not directing and you manage these things, that works too.
So that's how I approach these things.