Tip 1: When starting, some people find it helpful to use a soft Thumb Tip to build up thumb strength. In fact, many people who have mastered the LDS still use the Thumb Tip.
Tip 2: If not using a Thumb Tip, lick your thumb just a tiny bit, then rub it against your arm once (no more than once, or you won't have enough moisture for it). This will help a lot.
Tip 3: If your fingers feel sore, "cut up", and stretched out, try using just half a deck, then build up from there.
Tip 4: Pay attention to the angle of the deck. You want it pointing at about a 45 degree angle, and make sure the end of the deck isn't angled inwards or outwards- this will severely affect the aim of the card... and not in a good way!
Tip 5: Thumb position on the cards is very important. Play around with different locations to see what fits you best.
Those are just a few tips I would have personally found helpful when starting out. Hope I could help somebody out there!