Mario & Luigi: Superstar Saga

- There's a guy in the castle town who tells you about 10 gemstones buried around town. It's a pain in the ass to find them, but holy crap do it. The badge you get is probably end-game level equipment, and this is something you pick up about 1/3 of the way through the game. You'll need the Bros. Hammer special to find them though, you'll know what I'm talking about when you get there.

- If you want to brew all seven drinks, here's how you find all the beans: Green - enemy drops. Brown - hidden blocks (be especially on the lookout for these, they're of limited quantity). Pink - dig out of the ground (Bros. Hammer special again). Yellow - mini-game rewards. I'd do it too, you get an exclusive accessory for each new drink, such as double money, floating jumps (for dodging), and guaranteed item drops.

- You get a "bonus point" each time you level up, for a random increase in one stat. Don't use it on the same stat repeatedly, as it decreases your odds of a good number.

- Explore, explore, explore. Almost every place can be revisited with enough backtracking (there are warp pipes too), and the game almost expects you to once you have new abilities. You can get some good loot this way too.

- Use Bros. moves enough in battle to unlock Advanced forms for them. Watch for the exclamation point, hit the button for that brother, and follow along. They're good, and you'll want to learn them.

- Pretty much all enemy attacks have some sort of clue as to who they're targeting. It's a bit of trial-and-error but usually they're pretty obvious.

- When photographers tell you not to move, ignore them.

- Some bosses have unique items that rarely drop. Use the item you get for making all the bean drinks if you want them.

- Other than boss drops, the aforementioned gem-hunting quest and another one in the castle town where you find someone's pets are the only things I can think of that can be missed permanently.

- There are two Thwomps that will ask you to gamble. You can win a new Bros Attack from each one.