You don't find a true course.. you start with that as a know (straight line direction that you want to travel).

To fly a true course by magnetic compass you need to account for three factors. The difference between true north and magnetic north (variation)..   Compass errors caused by the plane itself.. airframe and avionics (deviation).. and adjusting for the wind.

That three-step process always bothered me, because if you fly any distance at all, east-west, the variation can change. The deviation is always some random thing that doesn't fit a neat, little formula to just account for as you change headings and winds aloft are never constant OR predictable (to the point that they'd apply to figuring your magnetic heading right down to the degree).  On top of that.. no pilot can hold a heading accurately enough to make it all come together.

What it all is supposed to do, is reinforce your spacial awareness.. get you used to thinking in terms that help you keep a mental image of where you are and where you want to be and how you don't just point a plane in that direction and go.

If you're about to take a test.. you've no doubt gone over this material and are just having a mental block. Go back and re-study keeping in mind that three-step process and why you take each step..

DoH!
Brett's answer is basicly 100times better than mine 

What you draw on the map is your true course.. What you end up flying is your track..

Think of course as want you want.. Track is what you do.. (hopefully they're close)

Brett, I've always been taught that you plot your TT on the map. In fact...I've never heard about the expression "true course"

But mind you, I'm educated here in Sweden...we tend to be a little weird at times  8)

Quote:

Yeah, we call it TC, and we plot it on our maps...

"I am from Shveden-isn't that vierd?"

  What tennm needs (or needed, I guess, at this point) is some help using the plotter to find the true heading of a straight line between A and B, which is known as "true course", "true track", or "truly just the path you'd like to take through the air". 
It's very simple, really- although I recall getting bewildered by it a few times early in my training. Assuming your plotter is like mine, you lay the bottom edge of it on your line, then slide it so the hole in the center is on a vertical grid line (longitude line; they're black lines spaced  half a degree of longitude apart on a US sectional) on the chart.
Remember- use a vertical grid line, not a horizontal one. Keep the plotter parallel to the line you drew... it can be touching at the bottom or top edge, or wherever- as long as its straight part is parallel to your drawn line and the hole is right on the vertical grid line.
  Your plotter should have two numbered scales, each with an arrow showing the rough direction of flight (to the left of your vertical line or to the right).
Choose the scale whose arrow matches your general direction, and where the vertical line falls on that scale, the number there is your true course, or true track, or whatever... think of it as your desired path, the line over the ground you would like to follow.
If you want at that moment to know what your course heading imight be going the other way along the same line, just look at the other scale... the number there will be exactly 180 degrees different. Amazing, isn't it?
If you are still unsure of what to do next, refer to Brett's post...