Ok the optifine mod cuts down on lag so here is the link to the forum post for all of the optifines. Make sure u always have the newest 1, it helps alot
http://www.minecraftforum.net/topic/249637-142-optifine-hd-a7-fps-boost-hd-textures-aa-af-and-much-more/
here are installation in structions
Manual Installation
Windows/Linux Instructions:
1) Locate your minecraft.jar file. On Windows, it's in %APPDATA%/.minecraft/bin
2) Create a backup of minecraft.jar
3) Open minecraft.jar in an archive editor (WinRar/7-Zip/etc)
4) Delete the META-INF folder.
5) Copy (drag and drop) the .class files from the downloaded zip file into the jar file, replacing previous files.
6) Run Minecraft and test!
There yall go
hope it helps