My pet hate is when newbies periscope their kites (i.e. hold directly overhead) - regardless of the situation....
...be aware of those kiting around you and position your kite accordingly. Standing with your kite directly overhead is never a good idea anyway due to lofting risk.
The only time you should keep your kite "high" is when you are passing upwind of a downwind kiter (who should be keeping their kite "low").
Its amazing how small a kiting area becomes when kiters dont follow these basic rules !
Another hate is when I come in from a run and kiters standing on the beach have their kites either overhead or over the water....for f**ks sake - either put the thing down, or have a kite