i used to think line movement, but even that is overrated. the magpies opened at something like 80 point favorites and closed at 70. they still won by like 100.
The penny is my biggest handicapping tool. I just flip it and if it's heads I go with the fave, if it's tails I go with the dog. Works with over/unders as well. Teasers and parlays are out.
Power ratings. I do my own and update meticulously. My percentage isn't even that great with them (I find that I have more success playing different "angles" and "situations") but I still refer to the ratings. It's a "security blanket" for sure, if my angles say the dog at +6 is good but the ratings say that dog should be +9 I back away. Helps me with the teams that I don't see much of at all.
I do all of my handicapping and then final pass through is wagerline. I adjust 1 unit either way on every game because of wagerline and will even make a no play into a small play.