How Do I Decide Where to Put Mountains?

[TombRaiderJake]

This is my first serious attempt at map-making and I have run into a major roadblock. How do I decide where to put mountains? I attempted making a basic height map (for reference only) by putting things in random places, but I am unsatisfied with the result. There's no reason to it and it looks unnatural. Without a height map, I am unable to put lakes and rivers in proper places.
This is the map that I'll use for the final product:
World v0_5.png
And this is my reference elevation map:
WorldElevation.png
*I only did the main continent, none of the islands are done

Other useful info:
--Using GIMP
--Land area is going to be 4,137,640 sq mi (a bit larger than Canada) on a planet that is a bit larger than Earth.
----Each pixel is 4 sq mi, 2 miles on each side

tl;dr version:
Where do I put mountains and other elevated land?

[TombRaiderJake]

Update: I've done some work with tectonic plates. I think I've just about got it, but feel free to add any other tips if you have them!

[BraveSirKevin]

I think most people haven't replied here because it's a pretty tough topic and most of us who've stumbled across your question don't really know enough to give you some sort of useful answer. I'd say you're on the right track giving thought to tectonic plates. You should probably also do as much reading on Orogeny as you can manage. Might be that through your learning you'll find something valuable to teach to the rest of us.

[EricPoehlsen]

What scale is that map? That would be an important information before thinking about mountains and tectonics ...