OptiFine is a common mod used for speeding up MC it gives you more options in video settings, Example: You can turn off animations for different things like lava or water. It also speeds up FPS and supports HD texture packs better.
How to install:
Requirements: Minecraft, OptiFine (obviously) and Winrar, WinZip or 7-zip (I prefer Winrar though)
2.GetOptiFine: (Ad link removed)
3. Go into the optifine.zip with winrar or any of the others that i listed above, you will find several class files and other things.
4. Minimize the optifine.zip and go to your start menu bar (the little windows icon on the bottom left corner.
5. If you are using windows xp on your start menu on the right there should be a program named run click it, if your using Vista or 7 type in run on the search bar and hit enter.
6. On run, type in %AppData% Make sure you type in the percents in front and back!
7. A folder will come up, inside it there should be a file named .minecraft, open it up.
8. Go to the folder named bin inside and right click the file that says minecraft, it should be a .jar file, when you right click it go to open with and click winrar, 7-zip or winzip. (By the way if something about a license thing appears just close it, it doesnt mean anything.)
9. There should be a file called Meta-Inf in the file DELETE IT!
10. Go back to your optifine .zip but keep minecraft.jar open, finish this off by dragging and dropping all the files in the optifine.zip to the minecraft.jar. Then close everything and launch minecraft.
There you have it thats how you get optifine, to check if it works simply launch minecraft and go to video settings, check if there are different video options.
Hope this works :D