Trade it against the traders and not directly on exchanges wallet like Coinbase.

The best place is using trading platforms. There are lots of popular trading platforms and almost most of them have an open market for ETH trades. Instead that I will suggest all trading platforms, try to research the platform wherein you are comfortable with the fees or you think that you can easily browse on their interfaces. On a side note, try also to research if they have good customer support as these days, that is one of the main problem of almost most trading sites even how reputable they are. And one important thing, take note of minimum ETH deposits as not all trading sites will allow you to deposit ETH in any amount you want. For example, Poloniex needs .5 ETH as minimum for them to be reflected in your account.