My flag placement depends totally on where I am shooting. My first flag goes 10 to 15 yards out. After that my flags go out at approximately 35, 75, 100 and somewhere between 125 and 150 yards. As I go down range to place flags I try to place my flags so they are not being blocked by trees or hedges. They will both allow cross winds and eddies. It’s those odd little puffs of air make the difference between 248s and 250s. 
When shooting with friends whose flags I know I will place mine in-between theirs so that the three of four of us can sample more wind. I can’t keep too many balls in the air at a time so by half way through the first day I have 3 or 4 flags that are telling me the condition I’m looking for and the rest I just monitor for major movement.
I always keep a quick eye out to the other flags on the range that are into the wind you can watch conditions travel across or up and down the range that way.
40 Rod

When I made my set of wind flags, set them up on lawn to try them out.  Wife takes a look..and says...Oh..wind callers!  Thats about right..just about every time I set them up at range..the darn wind picks up!  I'm the only guy at club using them..get some funny looks...but then, I'm the only one shooting cast in rifles, so they figure I"m just weird.

It's a good idea to use some sort of wind indicator with these slow moving old bullets.  It really doesn't take a lot to move them around and spoil a good target if you are not compensating.   

One of the ranges I shoot at has a ton of mirage. It's basically a 200 yard long rock quarry that is open on two sides.  I like to shoot there with just one flag at the line and mostly rely on the mirage.  It's very educational.   

Chris.

What I’ve always wanted to do is set up smudge pots that would let out a thin stream of smoke at 50 and 100 yards. Then you could watch the smoke.

40 Rod