Where/how do you get the info for placing trees? Also the suggested flight lines are often on signs.
From the customer, course designer, google satellite view, other source?
I'm curious.
I get sketches from the designer or club member or otherwise most knowledgeable disc golfer associated with the project. For many local courses I've mapped it myself -- fine example is Steeplechase in Kyle TX. I went out there blind, found some locals, played one round with them, and proceeded to play 4 more rounds until I had the place memorized. I took lots of photos, made myself a guide for where the tree clusters were, and the terrain and shot logic was from memory. I mapped all 36 at Circle R based on memory from hundreds of rounds.
At my original tee sign employer we developed proprietary hole sketch worksheets that helped get all the information represented in a clear manner -- I'd encourage any tee sign designers to make their own custom worksheets. That's the route I'd take again if the maps went very far beyond this complexity. I could source this type of map with napkin drawings and iphone pics. For the ultra-next-level style of signs I've developed over the years (not yet public) I'd want a video walkthrough to accompany a proprietary map.
Suggested flight lines are tricky and once or twice I've made that call based on the course's users. My default is to not force any shot logic like that. I remember doing a gated community's signs... it would be a majority teen-to-middle aged novice players -- there, some suggested flight paths were appropriate. For this course, I figure the players would have a wide range of skill and physical ability that would make for numerous valid smart-golf lines, which I'd leave up to them and their Coaches.
Part of why I use the "fairway" green shape is to encompass all the spaces and landing zones that would constitute a successful play of the hole. This serves to guide the player down the suggested path without explicitly saying "this is the valid way to play the hole". Also, you could go big over some trees and land in the "fairway" area... with just the green shape and no lines, this approach serves everyone. Also it makes it look a little more like golf, and shows an overarching game logic to an otherwise difficult-to-visualize strategy.
To sum all that up, throwers will mostly use the sign to make an informed tee shot. I wanna give guidance by making sense of the layout and terrain, showing spatial relations of seen and unseen obstacles, and ultimately let them decide on their line.