Even though fluency is mostly the combination of a lot of different skills, there are some ways you can practice fluency directly. Some are quite obvious, but you might not have pushed yourself in these areas before. Others are less straightforward but will become second nature with time and constant practice.
1. Speak more
This is mostly useful if your theoretical knowledge is higher than your ability to express yourself. You learn new things mostly by listening to others, but you can increase speed by speaking more. Since most students spend too much time with passive studying, speaking more is good advice in most cases. A great way to put yourself out there is to find a language exchange partner or take a trip to China.
2. Speak with yourself
One may be the loneliest number that you'll ever do, but we all find ourselves lacking conversation partners now and again. If you don't have enough people around to speak with, speak with yourself. This might sound very strange to some, but an important part of fluency is to be able to use Chinese to phrase your thoughts fairly quickly. As you go about your daily activities, narrate what you're doing and thinking out loud in Chinese. Talk to your pets in Chinese. While listening to the news or the radio, respond to the commentators out loud in Chinese. You will certainly get some practice by doing this on your own, regardless of whether or not someone else hears you.
3. Internal dialogue
Just as speaking out loud in Chinese to yourself is useful, try changing your entire train of thought into Chinese. You can do this more explicitly in several ways, such as counting in Chinese, describing what you're currently doing in Chinese or weighting pros and cons of certain choices in Chinese. As an added bonus, research suggests that decisions made in a foreign language are more rational than if made in your native language!
4. Language games
A major requirement for fluency is to be able to navigate around obstacles you find in your path. If you get stuck on every single word you want to say, you won't sound very fluent. If you can talk around these words, the listener might not even notice that you didn't know it. Practice this by describing words in Chinese without actually saying them! This will prepare you for an emergency vocabulary situation.
5. Vary the topic
I said above that if you can control the topic of the conversation, it's possible to rely on background knowledge, word games, and common filler phrases. However, this also speaks to my next point: often you won't be able to control the topic at hand, so you'll need a breadth of vocabulary to truly become fluent. Real fluency is about being able to talk about all kinds of topics with relative ease. To achieve this, you need to actually practice speaking about different topics. Over the course of the day, jot down different topics in a notebook or on flash cards. Work on digging up topics that you know little to nothing about. Pick a new topic to cover daily or weekly, and gear your language study towards that topic. Native speakers have had a lifetime to practice, so you'll need to start now and practice daily if you want to catch up!