Optifine is a mod that you can download and use. It's basically a boost FPS mod and it helps with running other resource packs and mods.

 

Just so you know, for some PC's, Optifine can actually cause more lag, but I would totally look into it.

 

@BackToThePast most of the computers will get less lag if u install optifine and btw @SpotlessBean you can check my thread: http://tinyurl.com/HowToReduceLag

 

For the best FPS also stick with a x16 texture.

 

I highly recommend getting Optifine as others above suggested, but degrading the texturepack (8x) will be a huge eyesoar.

 

Xray texture pack of course :) lol jk.

 

I actually think there are a couple of fps boosting texture packs. I'll post links if I find em.