Play maps that you can almost FC (less than 10 misses) and maps you can FC with 95%+ accuracy, in a few months time you'll be going back to old maps you did and ask yourself "This is easy, how did I not FC/SS this before?", that's what I did and currently still doing to improve. You'll naturally pick up patterns along the way. Accuracy is also a practice thing and it'll improve the more you play.
It'll also help if you don't play converts and stick to playing Taiko diffs only, though converts can help you get used to high/low SV.
As for determining how hard Taiko maps are, I look at OD, AR and Star Difficulty.