Sorry for the double post but I thought of something else. Consistency with commands is key. It took me forever to get my mom to use the same words and signals. For my dad I'm going to have to write them down because he doesn't get it.

"Down" is not the same as "Lie Down" to a dog. They don't speak English. I love the book
The Other End of the Leash because it explains something like a dog doesn't understand that "C'mere!" "Come" and "Over here boy!" mean the same things to us! Hee! Even your tone of voice matters. Hand signals work extremely well too. In some situations Loki won't *listen* but if I signal he'll obey.
For a cute example, my mom was trying to get Loki to lie down on his bed so she could take his picture. She's trying "Lie Down Loki" "Get in your bed" "Loki, in your bed" "Can you sit on your bed sweetie?" and on... and on...
I looked up and said "Loki, Target BED" and he happily went over and hopped on his bed. She thought he was only listening to ME, but really it's just that I knew the right command!