我还是不明白你的意思。

误：I don't still understand what you mean.

正：I still don't understand what you mean.

析：still 用于否定句时，应放在 don't, haven't, didn't 等否定词之前。又如：

He still doesn't understand.
他仍然不懂。

The breakfast I ordered still hasn't arrived.
我要的早餐还没有来。

I still haven't heard from her.
我还是没有听到她的消息。

When I came back at midnight she still hadn't finished.
我半夜回来时，他还没有做完。

I've been waiting for an hour and he still hasn't turned up.
我等了一小时了，可他还没来。

I still haven't thanked Aunt Lucy for her present.
对露茜姑姑送的礼物我还没有表示感谢呢。

I've been married to you for sixteen years and I still don't understand you.
我和你结婚16年了，可我对你仍然不了解。

注：有时 still 也可放在助动词与否定词(not)之间，但较少见，如：

A solution still hasn't been found. / A solution has still not been found.
还没有找到解决的办法.

但不能说：A solution hasn't still been found.