Here, before I go, I'll post the raw Top 10 list for you guys in the Retro Game Club with some quick notes. Hopefully you can figure out what I'm talking about and it helps a bit:
10.
Don't Worry About The Mallets - The centurions are a good idea, but the implementation isn't great. All the bosses are so easy that hearts are more useful.
9.
Kid Icarus: The First Game With A Morality System? - Basically, you can use the second controller to get cheaper items. If your Strength is 1 level above the current World Map, press A+B on the second controller to intimidate the shopkeeper into lowering his prices. Doesn't work on the Black Marketeer, though.
8.
Farm Yourself Some Hearts - I had a bunch of tips for heart farming, but I can't go into all that, now. In the early stages, it's worth it to take it slow, though, and farm hearts. You can also use the Healing Water in Fortresses as a home base for farming in nearby rooms. One of the requirements for the best ending - the one where Palutena falls in love with your rocking Adonis bod - is full hearts. So it's worth it to fill up at some point.
7.
How To Train With Zeus, You Weakling - So training with Zeus can be brutal. But if you duck down, just left of center on the platform, very few panels will actually hit you. Pay attention to the trajectories and quickly dodge or kill the ones coming toward you, and you can get out without being hit at all. Almost always worth training, unless you're literally one sliver away from dying.
6.
Stay Away From This Little Prick - Pluton shows up to steal your Zeus items in two levels.

More annoying than the Duck Hunt Dog, I assure you.
You can't shoot these guys, so get ready to dodge. If you see gravestones, Pluton is nearby. Which means he's probably a graverobber as well as a pickpocket.
5.
Make Sure The Eggplant Wizard Throws Flyballs - The EW's throw their eggplant projectiles in one of two trajectories, either low and slow or high and fast. High and fast is much, much easier to dodge. So, if you come across them, exit and reenter the room until they're throwing at the high-fast trajectory. Then go for the lower wizard, when you see an opening. He should be throwing well over your head at that point and should be easy to kill.
4.
Need Money? Learn How To Cheat The God of Poverty - The treasure room isn't actually randomized, and there's a method where you can decode where the God of Poverty is. Check out the
Kid Icarus Shrine for details. Look under "How to Crack the Code of the Treasure Rooms".
3.
The Kid Icarus Rule of 4 - Bad guys tend to come in waves of 4, and a new wave won't come until you've killed off every member of the previous wave. And a heart from an enemy counts as an enemy. So there are instances, particularly in the vertical platforming, where you can use this to your advantage, particularly if your life is low and you want to fight as few bad guys as possible. You can kill 3 enemies and just kite the last one, since dodging 1 is easier than dodging the next wave of 4. Or you can kill them all, but intentionally not collect the last heart to give yourself some extra enemy-free time. There are a number of minor uses of the rule of 4. Keep it in mind, particularly when your health is low.
2.
Make Pit Stick Like Spiderman - Personally, I think this is the most important raw gameplay technique, and failure to do this probably accounts for a huge amount of the frustration players have with Kid Icarus. You'll notice, Pit tends to have a little momentum when he's moving forward. He'll take an extra step when he lands, which can lead to "I'm Finished" a lot of the time. But you can actually cancel Pit's momentum. The most reliable way is probably pressing Up whenever Pit is about to land. He'll go into his Up-Arrow pose and, as a consequence, stick to the floor the moment he lands. Personally, I'm more in the habit of canceling Pit's momentum by simply pushing the opposite way I'm jumping right as I'm going to land. So if I'm jumping from left to right, I'll push the left arrow, just as I'm about to land. Part of me feels the Up Arrow technique is probably more reliable, but the important thing is to know you can cancel the momentum by using one of these techniques. Try them both out and decide which one works for you.
1.
Read the Manual - Am I the only one who never read the manual as a kid? Seriously, you need to know what the items do before you go into a shop. Just buying some random item because it looks cool is a waste of your money. While this game is not quite as dependent on the manual as Zelda, 5 minutes of reading it will save you a lot of wasted energy down the road.
Anyway, I had a long, hopefully entertaining version of those that is now lost to the evils of electricity. Hope these help. I'll clarify if anything comes across as vague.
Also, a plug for "
The Fall of Kid Icarus", because I spent a lot of time on it.