How to do a Minecraft Mod?

Ive tried and downloaded so many mods for minecraft and none of them work. I use a new .minecraft file everytime so that isnt the issue. Most of the mods say to delete the META-INF file so that you dont get a black screen? I tried that and I still got a black screen? Some say that after you move the files to the minecraft.jar you should only delete the two mojang files in the META-INF and that still doesnt work? So what should I do now. Ive tried to get the planes mod, wolf mod, vehicles mod, shelf mod. None work!