I would also be very considerate of posture, especially as you are learning. Eventually, the posture you select will become second nature, so it's important that you select one that is not going to cause damage, or pain. I would suggest an active posture - one where you have to focus, in order to keep yourself in the posture would be best. Then, if your posture slips, you'll know it's because your attention is elsewhere, and you can bring yourself back into your body.
Finally (because I have to go, not because I have no more to say) consider doing short length meditation at the start. You want to do 20 minutes, twice a day, but it doesn't have to be all at once, at first. In the morning and evening, set a stop watch, and let it run, until you feel you can do no more. Then subtract a minute or so from that time, and set a timer. For the first week, start the timer, sit with yourself, and when the timer goes off, get up, stretch, move around and do nothing strenuous for about a minute, then sit back down and start again, until you've done the equivalent of 20 minutes. After the first week, increase the timer. Just keep increasing it as you get more comfortable, until you can just sit with yourself for the full 20 consecutive minutes in the morning and evening.
The key is to not beat yourself up about not being "good" at meditation. When you realize your mind has been wandering, take note of it, return your focus to your breath, and move on.
A crutch is good for you as long as you stop using it when you don't need it anymore.
It works well with my procrastinating mindset because, even if I miss a day, I never do not boomerang the email to myself. It's important to learn to forgive yourself if you miss a day, which is why it works for me.
I also always zero my inbox which means I can't miss the email.
Your mind will wander, don't judge it, it's not good or bad. Just notice that your mind wandered and then focus on your breathing. Keep doing that until your time is up.
You shouldn't meditate with the goal of not letting your mind wander, and noticing your mind wandering isn't a bad thing. Just meditate by deciding to bring back your attention to your breath whenever your mind wanders.
I'll look into the Tara Brach podcast as well though. More opinions never hurt.
It's an open-eyed moving meditation. I love my 90 minutes of tech-free simpleness where I don't think, just react.
I can't recommend trying for 3 days straight enough.
When I developed more focus, I stopped using Headspace, so I could have longer periods of uninterrupted silence.
Try to only focus your awareness on the part of your body above your eyes. Something that helps is to pretend like you are carrying a basket on your head.
Also look for meditation MeetUps in your area, maybe being in a group will help you.
Meditation for skeptics.