Stop mindlessly singing through songs. ABSOLUTELY stop singing along with cast recordings. No one wants to hear your imitation of someone else. That = BORING. Have quality accompaniment recordings made for all your music (I offer this service for free in my lessons). Having tracks to practice with allows you to make original choices, and be musical in a way that is motivated by your interpretation of the text. It is fine to watch videos of stellar performers for ideas, and to let that shape your concept of quality work. Just don’t sing along with them repeatedly. That builds muscle memory for you to sound like someone else. Instead, encourage yourself to be the unique and amazing individual you are.
Be intentional in your practice, know what you're working on, why, and break your music down into sections and work those sections. If you have technical obstacles to overcome, that is best addressed with specific vocal exercises on a daily basis, slowly developing the coordination you need, rather than attempting to sing a section of a song to death in a single sitting. Every time you sing you are reinforcing learned behavior, so some of each practice session should be focused on introducing better and more helpful habits to your default sound.
Monologue your songs, until the words flow off your tongue like normal conversation. Speak them first ala “stream of consciousness.” Then, explore the punctation. Learn the notes on a neutral vowel, and then add in the lyrics without being constrained by the rhythm. Next, speak the text in rhythm over the accompaniment. Repeat yourself, to make sure you know exactly what you’re saying and what it means. Explore. Do more, think less. I once had a teacher say something to me that I never forgot: Think, THEN sing. Don't think AND sing.
Warm up your body physically before and while singing. Whatever type of sound you wish to produce, being physically energized and flexible will help tremendously. I like to move through yoga poses while singing, or practice Alexander Technique. I also like to find a physical embodiment of the journey that the character is on. Singing well requires energy and energy requires some kind of movement somewhere. Whatever I’m doing, when I’m practicing, I’m almost always moving!
90% of your practice time should be spent with the aim to not push your voice in any way. Go for complete ease, even if you crack, flip, or have to take extra breaths. The way you get better is by conditioning your body to work with efficiency and ease, not force. This doesn’t mean you shouldn’t explore your limits, but that is reserved for the other 10% (and then it is ESPECIALLY important that you are connected to the meaning of the text). Singing is more about coordination and less about strength. You need to practice the parts of your voice you aren’t so comfortable with. That takes discipline. However, it will pay huge returns.
Take breaks from practicing (several days off can be good), get enough sleep, stay hydrated and healthy.
But the biggest thing is - actually practice!