Dima Thefencingdude Lukhtai said but you can also use a mod like optifine to change various features to make it faster.
You could also write a batch script.
To mahe a batch file open Notepad (NOT Wordpad) and click
save as... and change the file type to "all files". Call it Minecraft.bat and click save. Now type this text into the file:
java -Xms1024M -Xmx2048M -jar "C:\Users\Yourname\PathTo\Minecraft.exe"
-Xms1024M is the minimum amount of RAM memory to give minecraft and the -Xmx2048M is the maximum amount of RAM to give minecraft in megabytes.
"C:\Users\Yourname\PathTo\Minecraft.exe" should be the location of your Minecraft.exe, this can also be just
Minecraft.exe if the batch file will be in the same directory.
Now save this file and double click it. A command-line window should open. Leave this window open and Minecraft should launch. Now just use minecraft normally but don't close the cmd.exe window as it will close automatically once minecraft has closed. Remember that you can only give minecraft more memory if you have that extra memory, in your computer, to give. If you do not have that extra memory minecraft will crash.