Step 1: Decide what you are going to work on.
Step 2: Get a timer.
Step 3: Set timer for 10 mins.
Step 4: Only work on what you need to for those 10 minutes.
Step 5: Set timer for 15 mins.
Step 6: Do something fun.
Step 7: Repeat steps 3 through 6 until you have finished what you are working on.

The main thing is to stay focused on the task at hand for 10 mins at a time. You might need to find a room where you can be by yourself and have no distractions.

Once you master 10 mins you can start increasing the time by 5 mins. I can do around 30 mins of work, before I get totally distracted now.