You've picked your subject, you've planned your time, you have your materials and now it's time to start teaching. Yay! Knowledge!
Before you do anything with your child, consider their "needs." In education, there's constant talk about Maslow's Hierarchy of Needs. There's a lot of depth to it, but one of the basic premises is that a person isn't going to learn well if they're hungry or tired, or have some other pressing need. So you need to think about these things with regards to your child. Don't try to teach them for the first time right before lunch or right after a vigorous PT session. I also think it's good to think about positioning. When we first started doing flashcards with Charlie, I had him look at them while lying flat on his back--that way he didn't have to worry about neck control, trunk control, etc.--he could focus all his energy on looking and listening.
It's also important to make this enjoyable. DON'T look at it as "if this doesn't work, my child is doomed." That's a recipe for disaster. Just tell yourself that this will be a fun experiment--if it doesn't work, you've lost very little. I have a silly congratulatory song that I sing when we finish a set of cards and Charlie loves it. Studies are finding that happiness can actually trigger the chemicals in the brain that aid in learning. My husband always tells Charlie how smart he is after a session. How great is that? We have activities that flop ALL THE TIME. I just keep pushing on and if it fails, then no harm done. I'll try something else next time.
You also need to keep it short. Flashcards should be shown at lightening speed. Every time someone sees me showing Charlie cards they say, "that is WAY too fast." You know what? they're wrong. I'm actually getting good at identifying this stuff and I have some of the worst memorization abilities of any person on the planet. Quick! quick! Little kids bore easily. Keep activities short too. You should have lots of repetition built into your week so no worries if things don't go perfectly.
As a final thought: remember what you're trying to teach. If you want your child to know that air planes fly in the sky, say that. It's not necessary that they use their arms to make a plane fly in the sky--that's a gross motor issue. They don't have to cut out the air plane shape--that's a fine motor issue. If they can do these things, then great! get them moving, but if they can't, that doesn't mean they can't learn.
Pictures taken a local event for families of special needs children and adults. I'll admit I had to sing to get this smile, but Charlie did great at an event that was full of people, loud noises, and plenty of commotion. Slowly, but surely he's getting less shy. He even rode an adaptive tricycle!