--Make you hack have sense
Do not make things that does look messy, like water tiles floating in the air.
--Check for Yoshi Coins
Do not put more or less than 5, must be FIVE.
Do not put for example the underground music in a forest or vice-versa.
--Put Few Bonuses
Do not put to many bonuses in a level. If you have to put one, make it well hidden.
--Do not Abuse of Bonues
Most times bonuses are a level plenty of coins and a few lifes. But do not fill it with 3up moons (and much less of 5up blocks!
--Compare Level Name w/ Layout
Compare if the Level's Name is like the level. It will be very stupid idea if you name an level of "Forest of Doom" and put an hearts BG and smile flowers at ground...
--Powerups? A Few too
I've seen many people puting 5 Capes just for jump a little pit, and 10 Mushrooms for kill 3 Goombas. Do not abuse of powerups, put 3 or at max 4.
Now I leave my IPS patches of my hacks for everyone play and edit as you want to.
Bramble Invasion & Surreliatus