Get your miles up to where you think you can hold it during the majority of your season, and once you are there you can do some tempo work at about 35-40 seconds per mile over 3200m pace or about a minute per mile over your current mile race pace. The effort should be moderate, not hard. If in doubt, do a bit more mileage and less intense running in the off-season and transition to the season. Here are some pace guidelines for you:
Run most of your easy mileage at 3200m pace per mile divide by .70-.65. So, if you can run 10 flat for 3200m now, then your current easy pace is 10 / 2 = 1 mile time of ~5 minutes / .7 to .65 = 7.14 minutes (7:08) to 7.69 minutes (7:41). Your faster distance runs, but not tempo runs, use about .75 and for tempo runs, once you are ready, use .85. good luck...tinman