How do I make minecraft mods work while playing it?

I have winrar and all that and i deleted the meta thing but when i go into minecraft its just normal and im confused. How do i activate them in the game?

 Ansver:

Some computers that don't have special prompts ( If you know what I mean ) do not allow mods to be in minecraft. Even if you have ModLoader , Forge or anything else that helps mods. Even if you download something simple that doesn't need anything. Textures might work but Mods don't. Try using another computer. That'll help. Secondly try updating minecraft. There are millions of videos that show how to do it. Try going to the forums and contact the mod maker as it may be a bug. Or it may be a activation key. Like Too Many Items mod you have to press 'o' to activate it. Make sure the mod is up to date. Like Optifine mod for 1.4.5 when you have 1.4.5. DO NOT DOWNLOAD Optifine Mod 1.4.2 for 1.4.5. as It might crash your minecraft or it might not work. Installing Modloader is also a great choice. or Forge. I have many answers but most people have already answered them. hope I helped

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This differs from mod to mod, but let me try and explain this to you like this. Lets use a really bad metaphor of typing a document. Deleting the META-INF folder is like opening up Microsoft word. You prepare yourself to type a document when you open up word, but if you don't type anything you don't have a story/whatever. When you delete the META-INF you are saying that now you are ready to install mods or type your story in our metaphor. Now in order to install the mod you have to read the direction of the specific mod. Its different for all of them. However, most require you to download the mod and then drag it into the minecraft.jar (the place where you deleted META-INF). Another common way is to drag something called modloader in that folder. Once you run it once, it will generate a folder called mods. Then you just drag the mod into that mod folder. I hope this helps and remember that you can also use the magic launcher which is a program that semi-automatically installs your mods. Just always follow the modders directions. http://www.minecraftforum.net/topic/9391…
ALSO please be careful with the link that Austin has put up there, its not the official link and minecraftmine is often times a dangerous site.

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1.Are you using up to date mods? For Example, Zeppelin 1.2.5 for minecraft 1.2.5. 2.Try updating minecraft. 3.Are you REALLY sure you installed the mods correctly, 4.Do you have modloader?