In reply to Sleepymouse:
Take the path from the Ogwen valley to Llyn Bochlwyd and from there to the col between Tryfan and Glyder Fach. Turn left and head up the south ridge to the summit.
It's in no way extreme, but I have seen nervous walkers intimidated by it so I'm not going to say it's a stroll no matter how much of a jaunt most people find it to be. It's nowhere close to being as difficult as an alpine scramble and it's scarcely difficult enough to call a scramble; if you're used to mountain tracks you'll wonder what the fuss might be.
The north ridge is a little more awkward. Though you can vary the route pretty much at will to seek out harder or easier lines as you wish, there's a move at the top which you're going to have to do. It's more awkward than difficult, a couple of steps downwards facing the rock, and again you'll have done much worse elsewhere.
So keep a steady head and you'll be fine. Whichever route you take, Tryfan is a splendid hill and well worth getting to know.
T.