I'm doing NaNo this month and am doing pretty well, I think. I'm definitely going to get to the 50K, and quite possibly even more. But as I've been writing, I keep getting stuck on how much detail to go into, especially around describing people and things. My book is set in an alternate world, so things are not going to be familiar to modern readers, but I feel like I may have been going a little far with detailing things.
Do you have any advice?
Over-describing is an easy pit to fall into and one many writers struggle to get out of. Especially, as you mention, when you're writing an unfamiliar world. There's always a temptation to make sure your readers understand and see the world as clearly as you do. But in reality, you need far less than you think. Readers' imaginations are wonderful things and should never be underestimated.
When I'm writing, I always try to make sure any description I give is warranted or that it can pull double duty in giving insight into a character as well as describing a place or object. For example, describing a character's shoes as meticulously cleaned Jordans tells you the character is probably both careful with his appearance and has enough money to buy name-brand footwear.
If a person or place is incidental to the story and will not appear again, then there is no reason to go into much detail. Be sparse and generic and move on, saving your more detailed description for a place that is central to the plot or a character you want the reader to remember as a policeman, or describing an office building as being a high-rise. Those few words can orientate the reader enough that they will understand the scene without going into any unnecessary detail.
Nothing stops the action as quickly as a long paragraph of description, so try to scatter your description throughout the text for the reader to pick up on as they follow the characters through their journey. This is especially critical in the early scenes of your book where you are trying to propel the story forward, introduce your main characters and hook the reader enough that they will keep going. Once you've got them into the story, there might be an opportunity for some longer passages of description if needed.
This can all be fixed when you edit post-NaNo, so don't worry too much about it as you try to reach that 50K goal. Right now you just need to keep writing.
Hopefully that helps!