1) How long did it take to break 70? If it took you 2 years, was that 2 years from the first time you picked up a golf club, or did you just play around for the first year and then take the second year seriously?
I started playing when I was 10 years old & was instantly hooked. I would hit balls with my dad's 5-iron at a nearby field, but here was the rub - he was right-handed, I'm a lefty. So I would turn his club upside-down with the toe on the ground & hit balls that way. Taught me creativity. I honestly do not remember the first time I broke 80, but it was somewhere around the age of 15.
2) What methods did you follow? Did you pick and choose from different instructors, books, DVDs, or even just watching tips on the golf channel? Did you follow a single set method/book/DVD/instructor and follow it like it was your bible?
I read two instructional books - Ben Hogan's Five Lessons, and Jack Nicklaus Golf My Way. Ben taught me technique ("Plane of glass", the grip), and Jack taught me course management, for example, learn to eliminate one side of a hole thru grooving a consistent shot shape.
3) What does it take to score in the 70s consistently (in your opinion of course)? A consistent swing? A good mental game? 70% mechanics 30% mental? Please share.
Certainly you need a somewhat solid, repeatable swing to break 80 - something that gets the ball on or near the green in regulation. From there it's all short game, and I've always thought that was the key to breaking 80 - a solid short game. If you want to break it down to numbers, here's how I've always looked at it -
If you can hit half of your greens in regulation, those will take care of themselves. You'll be no worse than even par on those holes.
If the half you miss, if you can get up & down half the time, there's 4-5 pars.
That leaves 4 or 5 bogeys on the remainder. That's 76 or 77 at worse.
So I believe the majority of practice time should be short game. For every hour spent hitting balls with full swings, spend two hours chipping & putting. Be bulletproof with six footers...the confidence will spill over to other parts of your game.
Re mental game, I believe the better you get the more mental the game is, so it's hard to quantify it in terms of percentages, so look at it as a sliding scale of percentage. For a 100-shooter it's probably 90% mechanics & 10% mental. For a par shooter it's the opposite - the mechanics are good, now it's a matter of managing the course, which is all mental, so it becomes more like 10% mechanics, 90% mental. So wherever you are between 100-shooter & par shooter is where you would be on the mechanics/mental continuum.