LOS woes

[Imp]

If your talking level terrain you have to try & figure out if theres a straight line of clear terrain, any part of a higher hex like trees will block.
Slightly raised terrain like fields high grass depends on visibility & vision aids if MBT how many you can see through, same for orchards, normally 2 or 3 for high visibility.
Dispersing smoke/dust is similar.
High ground there will be a formula for blind hexes created which you get a reasonable feel for.
2 hexes from the crest line not that much is blind to you 3 a lot is may not be able to see any level zero but can see some at higher elevation, you get a feel for it.
Treat woods as 1 level higher if they are at level 1 you really need to be at level 3 to see over & down. Comes with practice but you will still get it wrong quite a bit, know theres a good position round there just have to find it.
Suppose could try setting up a hilly map in the editor & place units around the map to see what they can see.
Think real life if you are at level 4 looking over a level 1 hill near buy it wont hide much. Move it away or increase it to level 2 & it hides a lot more.