Minecraft Random Lag Spikes?

It might have to do with your CPU, or RAM, perhaps your graphics card or a combination of the 3.
Minecraft lags when there are too many particles on the screen that it is processing. Turn off particles in the options menu.

If this is your first time experiencing this, then there probably a lot of entites loaded on your world.

If you've never experienced this, then if could be that your processor can't process all the information that Minecraft is displaying.

If your computer is good enough to play the game, then check your task manager. If your RAM and CPU is being used like crazy, try to end some unnecessary processes to help load the game faster.

Turn off the clouds, the block shadows(if in 1.8.x) apply your graphics to Fast, turn off your particles and put the max FPS to infinite, this should help you out.

Its gonna happen. It happens to everyone. Try to get a better connection. Try hooking up a lan cable to the computer you're playing it off of.