Well 99% of my fanworks are transformations of other peoples works. So my process is probably really different from other peoples. For every podfic I create I also create artwork for it and find music to accent the intro and exit of the audio files. So their are processes for those as well:D
Firstly, I am completely 1000% inspired by reading the original text. I usually know within the first few minutes of reading a fic, if it is something I could easily read aloud and act out. I get inspired by reading really good dialogue and will actually stop the reading and say them out loud to see if I can easily find the character voice outside of my head and if it will translate to me narrating it. I will read whole passages throughout a fic out loud to myself during the initial read. I read on my iPod so I have a TO PODFIC subfolder in iBooks that I immediately shelve to, so I can seek author information from there. I'm really attracted to fics where there are only 1-3 main characters and I will fiddle around with them to find the right voice for each before I record them.
After picking a fic, I go and research if they are blanket authors or if I need to ask permissions. Once I've received that, I do a final read through before I get the mic out. I then do the recording in GarageBand and upload to Audacity for editing. I do a first edit where I do like 90% of the work. My first job is scrub the file for background noise and then I expand Audacity and text and edit each sentence. I also silence all my breaths and play with pacing during the first edit as well. By the time I get to the end, I've done almost all of the work i will have to do for the editing.
After the first edit, I do a final listen through and find any issues with missed edits/dead noise spacing etc. While I am doing the listen through, this is when I typically create my coverart. All through the process of prepping for the record I'm diligently looking for screen caps or pictures I could use for covers that I save to a folder that I designate for that podfic. I store the text, raw files, art, music ideas into this file and refer back to it a lot. I then open up Photoshop and create the art and let the audio inspire me while I'm editing the art.
Once the final listen through is done, I add in the music last. I usually pick music by listening to peoples 8tracks fannish playlists. Sometimes an idea just hits me while I'm in the editing process and I try and find youtube instrumental songs to rip and use. Sometimes I just use key words that match the feeling of the fic or I try to find a song that's lyrics match the theme. Sometimes, it's literally one word that fits the story and I go for that. I pick on a whim sometimes. The one thing I try not to do is pick a popular song currently on the radio. This is a nod to my years working in movies, and knowing that picking a topical song for a film soundtrack is actually a kiss of death and unfairly dates it.
While I'm working on a project I'm 100% dedicated to that fic and live and breathe it until I post it. I sort of isolate my brain and become monogamous with that fanwork until I know it inside and out. It's sort of funny and sad, tbh.
The only time I really get blocked is when I go to record and within the first few minutes I realize it's not going to work out and I scrap the project then and there. Sometimes it just doesn't click. There's really nothing you can do when you can't make the voice in your head match the performance coming out of your mouth. For me anyway. Then sometimes I also get blocked while I'm editing and I have to just take a few days away from it. The editing process can be so tedious for me, all I want to do is chuck my computer out the window and set my hair on fire. I also get blocked by third parties on occasion too. I live in an apartment complex next to an air force base. So I've learned the only time I can be productive with recording is really late at night and really early in the morning. From like noon-ten pm is my blackout time. Nothing productive happens during those hours because of the outside noise.
I'm not really sure if this is what this day's challenge was asking for, but that is my process. It's basically my gut that tells me what to record and strategically knowing when I can be the most creative. Being diligent when I have a self imposed due date and knowing when to take a break for my own sanity. :)