I use maya but that's just what I was taught. Here's a quick run down of my technique for cars.
First up get your blueprints up and running. Take your time don't fuck it up, screwing this up will make things harder.
Ok, first thing is to switch to your side view. Zoom in nice in the front wheel arch area. You see that really small almost flat edge that goes round the inside of the arch? That's our starting point. Draw a cv curve following the edge, try to keep it central. Don't put too many cvs in your curve. Try to keep to as few as you can while following the shape.
Ok so we got our curve looking good from the side. Now use front / perspective to line the curve up in that axes. Once that's done, draw a plane below your first cv of the curve, try keep it the same width as our edge. Now select the top edge, extrude and tick selected curve. In number of sections try something like 9 or 11, you don't want loads, just enough to get the shape right. Once extruded, delete history and line it up nice with the edge on the blueprint. From there, you'll basically extrude the entire car. It's a neat technique and works on most vehicles