stare at your crossbar or grips. it helped me alot.
also, it is much, much easier to do it off a ledge/stairs or a bank than it is to do flat. i can usually truck a 5 stair first try, but flat it takes me like 3 or 4 tries. just saying.
when i do them off things, i throw the bar, then do the 360, but flat i throw the bar right before i land.