800m base training

give yourself a couple of weeks after cross country... (If you are doing cross country) and start by running at least 3 miles every day... no more than 6. Do some (3-8) 150-300m strides after each run at between 800-1600 pace depending on how tired you are or aren't.

Every week or two expand your limit on your runs... (E.G. now its no less than 3.5 miles and no more than 6.5 miles)

It sounds like you are a sprinter and if the mileage starts to beat down on your body take a different approach... don't get injured in the pre season!

Work on a lot of lactate tolerance. Not only is high lactate the bane of 400m runners running the 800, but I high tolerance is very beneficial in the 400m as well as the 800m. My favorite session is 2x4x200m @800m goal pace (30sec/10min). it's a Nick Symmonds special and I love it for learning how to push through the pools of lactic acid while also getting used to the rhythm of my goal 800m pace

This session should be done once a month. The rest of your days should be easy runs of 3-4mi. with a long-ish run of 5-6 once each week. On weeks where you don't have the LT workout, you should do 20min of diagonals (stride diagonally across a football/soccer field, jog the end zone, repeat) Focus on form during these diagonals. You get your aerobic work while also building strength.

100 mile weeks with 26 mile long runs and strides

For the 800 I usually just make sure to do 800 squats a day because that makes my muscles big and

big muscles=Big SPEED

Run the last half of your 5 miles run slightly faster than you've been doing them and the first half slightly slower. Don't change anything else at this point.