Hmm... this looks kinda retarted when typed up, but anyways, this is what I had written on a summary sheet i found. I dunno if its helpful, but thought I might post it up.
If a = f(t), use dv/dt or (d^2)x/d(t^2)
If a = f(x), use d(0.5v^2)/dx
If a = f(v), use dv/dt if initial conditions...