I have trouble with things like synonyms so I try to make use of a thersaurus. I've not considered the strenght of words. That seems inspiring.

I also think non native speakers can actually become advantaged when it comes to testing on English. I'm told a lot of natives don't touch the basics for a while so it seems I did better than a lot in the standardized testing of English simply because it is fresh in my mind. If you hear me speak though my minor accent betrays that I wasn't born here.

That said, I struggle with idioms and colloquial expressions. I remember being confused with "pulling your leg". Living in the South East for a time, there is a lot of idioms and expressions. Seems like most of what southerners say is idioms that make no sense to non native speakers and probably even Northerners. I also think it helps that US movies are so prolific and immitation goes a long ways. Just don't trust the depictions of southerners. The sound is way off and over dumbified.

Also, I started watching a lot of UK tv shows. It seems to help me since they seem to have a wider use of vocabulary. They also seem to have less idioms.