This article is from the Obedience Trials, by Cindy Tittle Moore with numerous contributions by others.
Common handler errors:
1. Tight lead (loose pts for lagging AND tight lead) This could also
cause a zero for the exercise, if the judge feels that s/he was
not given an opportunity to see the dog work on leash
2. Adapting speed to dog (Especially not walking briskly.)
3. Not changing speed
4. Lead corrections
5. Not heeling so DOG IS ON MAT
6. Stepping into dog on sit
7. Too many steps on the halt.
8. Anticipating judges commands (going back to normal after the fast
before the judges command, turning early, etc)
9. Pausing or stopping on about turn (heels should never come
together - the turn should be made in motion)
10. Rounding corners on the left turn to avoid crowding by the dog.
11. Checking each sit after the halts
12. Extra body movement on the "Heel Command"
13. Moving the leash position after starting to heel.
Helpful hints:
1. Don't stop too quickly on the halts - many handlers panic when the
judge commands and they stop on a dime.
2. When the judge asks if you are ready, LOOK at your dog first
before you reply.
3. If the dog lags (i.e. on the figure 8) don't let out the lead, let
it tighten up - the judge will take a lag only (the dog caused the
tight leash)
4. Don't look back at the dog - it will only cause the dog to lag
more.
5. Many handlers forget to give the "Heel" command after each command
to "Forward" by the judge.
6. If you have questions, before the exercise starts (about anything
- since this is the first exercise) ask the judge.
7. Crossing the mat on the fast time. Crossing the mat is a problem
that occurs when the handler doesn't walk or run in a straight
line. Either the handler moves across the mat to the left (into
the dog) which seems to be more common, or moves across the mat to
the right (away from the dog).
 
Continue to: