Fundamentals historically obviously play a big part.... tightness in the physical cargo / barge markets, refinery shut downs etc etc. Suprisingly whilst having an effect on the term structure these have been having less and less of an effect effect on the flat price, or if they have it's gone in the opposite direction to what you'd expect!!! It's almost like the fundamentals are being completely disregarded. For example, build of about 10m bbls in the last 2 weeks according to DOE stats, yet flat price is strong today, roofing on the early Platts window.
Geopolitical tensions - Iran, Nigeria.
Agree with last poster - all the benchmarks are highly correlated. If you're trading brent for example, and you see a big spike of volume go through in WTI breaking new highs, then it's a good confirmation that the brent is going up too, etc.
But for me, it's all about the USD at the moment. Watch key levels against the EUR. The past few weeks with the Greece situation. Any little bit of news regarding that, e.g. comments from Germany's Merkel, have often moved the market
A few locals I know have pretty much stopped trading at the moment, because of so many mixed messages and such indecisiveness. It's a bit tough at the moment!