One of the best things that you can do now during the off season are to do 6-8x100 meter strides after recovery runs. Starting at your 1600 pace, progressively get faster each stride until you are running faster than your 800 pace. I also like to put on spikes for the last two strides to get my legs turning over fast.
Another thing you should be incorporating in to your training are hill sprints. Find a hill with a fairly steep incline and do 4-6x10 seconds sprints as fast as possible. Doing these will help you develop better running mechanics as well as help you develop better power and sprint speed.
Doing sprints off the fly are another very useful workout to develop max speed. Do 4-6x30-50 meter sprints. Give yourself a 20 to 30 meter acceleration zone prior to the fly zone where you can accelerate to full speed. Take full rest after each sprint (the general rule is to take a minute for every 10 meters you have sprinted). For example if. You are doing fly 50s take 5 minute rest.
If you incorporate these training techniques you be able to develop great speed that will allow you to get well under 2 minutes in the 800 and be able to close in longer races much faster. Once you get in to your season and have done sufficient endurance and speed training you can sharpen up into sub 2 shape by doing standard sessions such as 4-5x400 at goal 800 pace or 10-12x200 or 6-8x300.