Pick up words in one conversation and used them again in another

It's helpful to differentiate reading vocabulary and speaking vocabulary. For non-native speakers, most of them have greater reading vocabulary than speaking vocabulary. Namely, they had no problems to read difficult articles from Time or The Economist which require huge vocabulary but they used only limited words when speaking.

To excel in speaking English, it's unavoidable to increase your available speaking vocabulary. You should always look forward to learn new words and usages and be greedy on expanding the current size of your vocabulary.

An efficient way to increase your vocabulary is to copy what you hear in one conversation to another one. For example, if my native friends told me about his experience in ski, I would memorize around several words he used and repeat several times in my mind. According to my experience, these new terms automatically join my speaking vocabulary if I force myself to use these new terms the next time I talk to my friends about ski.

If you always keep this habit, your speaking vocabulary will increase steadily and level up your speaking ability.