Tips:
-Make a basic outline of the game's story
-Get a small testing group. Could be online people or people from school. It'll also help to make a FreeWebs website or even your own domain to organize your stuff better.
-Learn how to count in hex. You don't have to know how to translate, just know how to do very basic addition and subtraction with hex numbers.
ex. 10 - 1 = F
-Discover Diegoisawesome's XSE Tutorial and Seth's XSE Tutorial. Seth has a list of used flags that I refer to a lot. Diegoisawesome basically describes every single command. You don't need to memorize everything before making your game, just know how to start a script, compile a script, etc. Knowing how to use flags is great too.
-NEVER USE PERSON ID'S IN THE 2000'S RANGE. ONLY USE THEM IN THE 1000'S AND 4000'S RANGE. YOU DON'T EVEN HAVE TO IMAGINE THEY'RE IN HEX, JUST USE THEM LIKE NORMAL NUMBERS BECAUSE YOU ARE NOT GOING TO USE A THOUSAND FLAGS IN ONE GAME. (Sprites will reappear if you use flags in 2000's range if you setflag 0x[person id] after while)
-Know your limits when music hacking. For example, some tracks can't have music that's too long or have too many instruments.