To the OP - I think the post above is a bit harsh; considering the level of fitness you're at now and what you've mentioned about your past running, 6 months is a window to see a decent amount of progress in your mile time - but I think that you'd be better off aiming at 5mins, and if you are able to break your old PB that would be an accomplishment.
If you've run 126 and 317 in the past off of running like you're currently doing (7-15miles at a time), then that's a decent level of fitness for a recreational runner (I realize you may not be at that level now.) I think that if you want to try a baseline measure of 400m speed and mile time, as the poster above suggested, they are useful reference points. But maybe you don't need to focus on track intervals etc. to bring your mile time down. Over 6 months, maybe if in the beginning you focus on shorter runs with more speed (almost every day some kind of faster running) you can take a shot at holding a faster pace for a mile.
I've suggested this method once or twice before to new runners - I do think a goal of 40min runs, broken into 10min segments of faster and slower paces will help you initially - 5min easy jog 5min up-tempo x4, increase the tempo portions, decrease the jog time by 1 minute each week or 2, do this every time you run (4, 5 or even 6 times a week) for a period of 2-3 months. Up-tempo is purely by feel, don't worry about your pace, just let your body carry you, start in control and finish strong. If you find you can do 5-10min jog warm-up and then 4x 9min up-tempo/1 min jog, you will have improved your running fitness more that you realize. If you're feeling good after 4 repeats in the 40min, maybe add a few minutes and try "zen" intervals, where you are running faster (not sprinting or striding, but faster) for a certain number of breaths, focusing on your breathing rhythm (in for 2 strides, out for 2) - count 30 breathes in to start, take as much recovery as you need. You can increase the number of breaths you're running fast at if you like this, and decrease the recovery jog to an equal number of breaths (this will touch on building speed a bit.)
Then, after a couple of months like this you can start typically timed/distance intervals, mixing the shorter ones (1min or 400m etc.) with longer ones(timed ladders, mixed distance intervals etc.) This is after you have reached a baseline level of fitness where you have done faster running at a pace which you can handle and build on for your mile goal. This is also where you might be trying to set up a schedule a more serious runner might follow, and you'll be needing much more wisdom from here. If you are going to write about the experience, moving from the build-up to something more like miler training would be an interesting thing to illustrate for readers. You could try typical miler benchmark sessions of 10x400m, or speed-endurance focused sessions like 20x200m. A nice session to test yourself if 1600m-1200-800m-400m, with decreasing rest between intervals for building fitness (4-3-2-1min) or keep the rest the same (maybe 3min) for a test of speed endurance. This kind of thing has a very different mindset from recreational running, and maybe this transition (and the whole process) is something you can document and turn into a read.
Whatever you decide to do, I do think it is a matter of running as often as possible, but going by feel and making sure that you hit faster paces in every run (since I assume that over a 6 month window with your goal you won't want to focus on higher mileage.) For beginning runners, I think almost everyone who is reasonably fit can go through a period of rapid initial gains, and for you specifically you can also see improvements in 5kms and 10kms as well (faster than your half marathon pace, I'm sure.)
Good luck, and have fun with this. I envy you - this has worked for me in the past but my knees won't let me run any more.