If you want to get good at speaking a language, you have to start speaking it. There is no substitute for conversation practice. You can study the rules of syntax, semantics, punctuation, and pronunciation for decades, but you will not be able to speak if you never practice speaking. Imagine learning to fly an airplane by reading a book on aviation. You won't get a feel for how to operate the controls until you actually sit in the cockpit and do it. Language learning is the same way.
The sooner you begin trying to speak in your target language, the sooner you will be able to speak, so don't wait to dive in to conversation practice. Speaking your target language can be just as scary as flying an airplane, but a failed conversation is significantly less hazardous than a failed flight, so don't hold back!
One of the common objections I hear from people is that they're not able to start speaking until after they've already completed some amount of learning. This is actually not true. If you have a patient teacher, or friend who speaks the language (and I'll cover some good places for finding native speakers in the resources page), you can start your conversation practice right from day one, before you've even learned a single word in your target language. That's how Tom Cruise's character learned Japanese in The Last Samurai, while living in a village with no other English speakers. The clip below shows how simple it is to start with concrete words like nouns and verbs. In the movie, he progressed from the most salient words like bowl and chopstick to progressively more advanced parts of the language. Of course, this scene is from a fictional movie, but it's easy to imagine how this same process could be done in real life.