What is the best way to improve your Hebrew?
The more exposure you get to Hebrew spoken by native speakers,
the better! Whenever you can- LISTEN!
You need to train your ears, as often as possible:
Watch t.v in Hebrew (not the news), listen to Israeli radio and podcasts, record a scene/bit you like, to an audio file, put it on an audio player (such as your smartphone) and play it over and over when you go for a walk/wash the dishes/go to bed… Repetition is a wonderful tool. Join a class of your hobby- taught in Hebrew and with Hebrew speaking participants, work with native speakers if possible, choose a more Hebrew speaking neighborhood to live in, make friends with native speakers, listen to Hebrew around you when you ride the bus, listen in restaurants and cafes, at the supermarket, on the street…
And anything else you can think of! Always be listening.
The list above includes many options for speaking practice as well. If it's hard at the beginning, don't give up. Be persistent. Keep trying and it will happen. Wherever you go, try to use your Hebrew.
Reading in Hebrew will also contribute to your vocabulary and to your general understanding and familiarity with the language and its structure.
LEARNING WITH A GOOD TEACHER:
Finally, there's nothing like one on one Hebrew lessons with a good teacher. In such lessons you are "forced" to speak, and your learning is active, most efficient and rapid. You practice both your speaking and listening comprehension skills very intensively, and in a supportive and professional environment. A good teacher will focus on your specific needs and help you improve every aspect of the language, in a structured and effective manner.
Everything else mentioned, supports this greatly.