Improving your lie or position by moving growing things
Your ball comes to rest under a tree, and it appears you have a shot. Only problem is a pesky limb interfering with your backswing. No worries; you can break that branch off, yes?
Nope: You cannot improve the position or lie of your ball. This includes moving or bending anything growing or fixed in the realm of your envisioned swing.
The two biggest infractions in the sand are grounding your club and moving impediments from the bunker. This pains me to bring up, but my high school coach made me call both infractions on a competitor in a match: He chunked his first bunker shot, causing him to slam his club in disgust. He then threw out a few rocks around his ball before attempting his next shot, both violations. If you thought he was mad then, you should have saw his face after I sheepishly told him about said offenses.
In a related note, we are not Facebook friends.
Rake in bunker
This is another area that causes confusion, but if your ball comes to rest against a rake, you are allowed to move the tool, as the USGA defines it as a “movable obstruction.”