If your focus is on 800m, then after you are satisfied that you have a reasonable base, you can run most of your workouts based on your specific target. The most obvious workout would be 2 sets of 3x400 at race pace with 60-90 sec rest.
My personal favourite, and one that I have found as an accurate predictor is 2 sets of 200-500-200 at race pace with 60-90 sec rest. Full rest in between sets.
Don't forget some full speed-5x200@400 speed. full rest.
Also, to make sure your shape is holding up, do a 1500m workout once every 10 -12 days such as 1200 + 800 +600 +400 at 1500 0r 3k pace with about 5 min rest.
Much depends upon your age and background. If you want a bit more specific advice I'll be happy to comment.