Adjust Game Settings
Changing certain "Minecraft" settings can help the game run more smoothly, especially if your computer is fairly old and barely exceeds the minimum system requirements. Launch the game, sign in to your account, click "Options" and select "Video Settings." Set Graphics to "Fast," Smooth Lighting to "Off," Render Distance to "Tiny," Clouds to "Off" and "Particles" to "Minimal." This will make the game look much uglier, but will have a positive impact on your FPS. Once you've done this, return these options to their higher values one by one to find a balance between graphics quality and FPS. Activating the "Advanced OpenGL" option may also have a positive impact on your FPS, although this is not always the case.
Close Other Programs
The more programs you have open, the less memory and computing power will be available for "Minecraft" to use. Before launching "Minecraft," close all programs you can, including your browser, and only leave essential ones running. Ensure you check not only your taskbar but also your system tray for running programs.
Ensure the Correct Version of Java Is Installed
Having either multiple versions or a mismatched version of Java installed on your computer can be a cause of low FPS. Click "Start" button, right click "Computer" and then select "Properties." Under the heading "System," you will see either "64-bit Operating System" or "32-bit Operating System" listed as the system type. Make a note of this and close the window. Open the Java download page (see Resources) in your browser, click "Free Java Download" and select the version of Java that matches your system type. After the installation is complete, navigate to the Java Uninstall Tool page (link in Resources). This tool will check for old versions of Java and remove them from your computer.
Disable Windows Visual Effects
The Windows 7 operating system includes visual effects that make your computer look better -- the problem is that these same effects can also drastically lower your computer's performance, especially if it's not very powerful. Click "Start" and select "Control Panel." Type "performance" in the search box and then select "Performance Information and Tools" in the list of results. Click "Adjust Visual Effects." You may be prompted for an administrator password. In the Visual Effects tab, select the "Adjust for Best Performance" radio button and click "OK." Doing this deactivates all visual effects to improve your computer's performance.