There are two(main) ways to install minecraft mods. I assume this is for Windows.
1. MCpatcher
To use MCpatcher, download it and then download modloader(unless otherwise specified). Download whatever other mods you wish to download, then open and install them in MCpatcher(modloader and other managing mods first, e.g. minecraftforge, HD textures, etc.). Afterwards, they should work. This also works with texture packs.
2. Manual
Click "Run" in the Start menu, then type %appdata% and click run. Click on .minecraft. Click on bin. Right click minecraft.jar, then open it with winRAR or some other .zip/.jar file opener. Download Modloader (unless otherwise specified). Open Modloader with the file opener as well and drag the files to minecraft.jar. DO the same with all the other mod's files and it should work. Note: there may be mod conflicts which are much reduced in MCpatcher.
All minecraft mods are free. If you find mods that cost money, don't buy them. It is either a scam, waist of money, or both.
Please Revise Question For Minecraft: Mods are the community managers
you can get minecraft mods and textures off the minecraft mods website.
Yes. Most mods in Minecraft are free, however you can donate to the developer to help them improve and make new mods.
It has a group of mods. Either you are on creative or you have your difficulty turned down in the settings.
fly mod
There are no cheats to minecraft. Sorry. But you could download and install mods that can help you get what you want.
bearshare is not required to get minecraft mods.
Yes, most Minecraft Mods are updatable.
there are no mods in minecraft pe i hope there will be
you can get most minecraft mods off the minecraft mods website, or you can google.
Unplug your hard drive and put it in your computer and get mods for minecraft