How are cheat codes in video games discovered or unlocked?

I just reinstalled the game onto my computer. I used to play it years ago and knew all of the codes. Now I forget most of them. Does anyone know of any good codes to use in it? I already remember “Rosebud” but that’s just about it. Also, anyone got any good sites where I can download Sims items for free? Before you all suggest The Sims 2 game. I’ve already had it. It wouldn’t go on my computer because I don’t have the proper video card for it.
Take Care everyone!

I want extra money for my sim and I just cannot figure this out. I know the code: L1, L1, R1, X, X, UP but when I do it, nothing happens. I see the gnome. Ive tried to click on him but I cant. I stand there and do the code and nothing happens. What am I missing? I am not a video game person so please please really dumb this down for me. Tell me EXACTLY what to do. I cant imagine what Im doing wrong so I figure it must be something so simple that real gamers wouldnt even need to be told to do it. Please help! Thanks

I mean it doessnt work for me,or maybe im doing something wrong? PLease explain to me what is it, how to use it & what does it do?

Thank You!
DO I HAVE TO PRESS ENTER AFTER PUTING UP THIS CHEAT INTO THE BOX???

PLEASE WRITE ALL BY STEPS!!!!
also I dont know where do I type it & when. All I know thar it doesnt do ANYTHING that it should do!

HELP! ;(((

I need a code to unlock the video poker game on Sega Casino for DS. Please help!