Help me improve please

I'd like all of your expert opinions on my first attempt at terraining.

I was bored this week (too much free time for "studying"), and thought I'd try my hand at some terraining. I used to muck about in StarEdit and the WC2 Map Editor a lot, but never came up with anything of note. Now I'd like to at least reach a reasonable level of skill at something in WC3 map-making.

I'd like some constructive criticism of this please; some pointers on how I can make interesting terrain. You never know, I might turn up something of interest one day....

how to become just generaly good here
for general tips, i tweeked the area where green and yellow start. just use those general meathods (proveiding you like the look)

Thanks Gitlich, I'll read the related threads. And that does look much nicer around the waterfall :)