It's a practice thing to a large degree. Like feline fanatic said, the really perfect ones are either done by people who have been doing it a very LONG time, or there's some sort of assistance (templates, marking, computer guided...)
Apparently I'm the opposite of Tartan - I find meanders to be pretty easy and feathers to be rather difficult! It really varies from person to person. I used to draw doodles all the time that was essentially tight meanders, so that quilting "pattern" comes very naturally to me. My feathers, on the other hand, still come out looking like mutant corn cobs! *sigh*
Marking helps a LOT, even if you just mark off areas to help keep your focus. I like to give myself "lanes" to "drive" my pattern through. That helps me keep my sizes consistent and make sure I don't leave big open spaces unquilted by accident, and also makes it so I don't have to decide where to go next as I'm working.