My main interest with oil painting is achueving a realistic effect. Not necessarily photo realistic but definitely image identifiable. Recently, In my Blue Still Life with Shell, I experimented with an impressionistic style, placing points of color in proximity to one another and I was quite pleased with that painting. My currrent pieces - several still lifes and pet portraits, while more realiastic, seem to be utilizing a little of that new flavor particularly when it comes to brushwork and color choices.
I usually begin my paintings by choosing a color for a toned ground to act as a foundation. Often I select a color that appears only sporadically in the finished painting, since choosing it for the ground will unify the painting. I then proceed to make a line drawing of the subject and transfer it to the canvas or panel using charcoal or graphite. For my realistic paintings, I then make a grisile - a monotone - either in greys or umbers, followed by layers of glazing for the colors. For the more impressionistic works I proceed directly with spots of color as seen, and eventually the spots come together as a whole.
I usually use commercial paint, but occasionally I grind my own pigments. I use both canvas and gessoed panels. I highly recommend the Gamblin line of oil paints and mediums. Their new Fastmatte line is wonderful for underpaintings and Grisailles. I also employ their Neo-megilp medium for glazing - a modern non-toxic version of the Old Master's Maroger Medium - to good effect.