Here's a quick example for you, since you're hand-drawing your map.
This is for a sort of gulley/canyon with a big river in it, but it should apply the same.
See around the edges, how there's black, then shades of gray, going up to white? The white's always going to be the highest point on your map while black will always be the lowest. Build up shades of gray between them to get a nice mountainy effect.