I've tried everything to get mods on minecraft. I never could get anything to work. That is... until I discovered the MagicLauncher. It doesn't hurt or damage you .jar and you can turn off the mods whenever you want. Now I'm going to show you how. Please enjoy.
Step 1: Download
Google Minecraft MagicLauncher and download the one on Minecraft Forum. It is the safest place to get mods. Also, you need to download the mod and/or modloader. I'm going to download the Portal mod and Forge. DON'T UNZIP YET!!!!!
Step 2: File Adding
Once you have the launcher up and running, click setup. You will see on the right it says add. Click that and it will open up the mods folder in your Minecraft folder. You can put your mods in there or somewhere else but you need to have the path to the zips on the file opener. Click the zip and then click open. Note: open the mod loader first, and you don't really unzip it when you hit open.
IMPORTANT!!!!!: FORGE WILL SAY 1 ERROR, IGNORE THIS, YOUR MOD WILL STILL WORK.
Step 3: If It Says No Mods Found
It it says no mods found. Then find where you put the mod zip. Unzip it and look inside. If anywhere it says put in .jar folder then look in that. You just need to find the .jar files. This is where you compress them and rename it. This should work, if not, I'm sorry, it is a faulty mod.
Step 4: Test and Use
Now after all your mods are on and they say that they are working, you can click test or ok. Test is just a test. Ok temporarily changes your .jar. To turn off mods, just click the check mark on the left side of the mods. Have fun and happy modding.