My biggest kickstart is freewriting; where you just sit with a notebook & pen and just write what comes through your head, whether or not it makes sense. Names of characters, what happened at work, what you want for lunch, the pen is just meant to be a faucet to let your thoughts flow out. It helps me filter out the flotsam and jetsam from the actual ideas I have. After I do that for 30-60 minutes, I usually have a good idea of where I wanna go with my writing, and then I switch to my laptop to write. (I swiped this from Tim Schafer in the Double Fine Adventure! documentary, and he said he was taught it by his middle school english teacher)
Another helpful thing is jumping around. Never be afraid to write out of order, especially if you have a good scene you want to write. It’s better to get it out and ride the momentum then be like “okay I have to save it I have to do these other scenes first.” Even if it makes some continuity hiccups you have to fix later, it’s always better to write something rather than be stuck.
Something I just started recently is writing as soon as I get up in the morning. I’m an early riser, and usually I take my time with like, making breakfast and then checking internet and such, but also I have bigtime motivation issues. But when I wake up and just sit on the couch with my laptop, I just see what I can do. It’s helped a lot! I may not be writing a lot, maybe like, a half page at most at a time, but it’s still a little progress as opposed to the zero I’d been making.
Currently I’m writing a wrestling themed ren’py game and I’m just chipping away at the outline I have. Like, just doing one section up to a decision point is slowly pushing myself forward.