How to make minecraft run with no lag?

Install optifine mod 1.7.2 (no forge needed)
Get a better graphics card.
Get more RAM.

If you have windows, run these programs:
-Disk cleanup
-disk defragmenter

After you defragmented and deleted unnecessary files off your computer, minecraft should be a lot faster.

I used to be able to run it without lag, i guess its just my computer getting old:

specs:

windows 7 64 bit
AMD E-350 Processor 1.60 GHz
4.00 GB RAM (3.60 GB Usable)
AMD Radeon HD 6310 Graphics

i just want to be able to run the game without lag on the lowest settings with possibly a render distance around 6 chunks
also i've tried changing settings to "best performance" in the advanced system settings and installed razer game booster

RAM DOES NOT ALWAYS FIX IT! <------ AND I STRESS THIS!
ANOTHER THING TO STRESS IS DELETING FILES ON COMPUTER DOES NOT AFFECT PERFORMANCE!

I can tell you a way to reduce lag and this works for me. I get steady 50-60 FPS on mac after usual 15-25.

1. Install optifine (I do it with kovacics mod pack).
2 Make these settings in video settings

GraphicsL Fast
Smooth Lighting Off Smooth Lighting Level Off
Fog: fast
Redner distance:6-8
Max Framerate: Unlimited
View Bobbing off
Advanced OpenGL: Off
Clouds: Off

In Details:
Clouds/trees/water/grass/rain&snow/Drop… Items/Translucent Blocks: Fast
Sun & Moon: off
Depth Fog: off
Stars: off

Animation:
All Off except Redstone Flame And smoke
Particles: Minimal

Quality:

MiniMap Levels: 4
Anistrophic Filtering: Off
Clear Water:/Better Grass/Custom Sky/Random Mobs/Better Snow/Custom Colors/ Snooth Biomes: OFF
Custom Fonts: On
Swamp Colors: OFF
Connect Textures fancy

Performance
Smooth FPS: ON
Load Far: OFF
Chunk Updates: 1
Fast Math: ON
Fast RenderL ON
Smooth World: On
preloaded Chunks: off
Dynamic Updates: off
Lzy chunk loading: on

Other:

Autosave: 30 mins