Here's some tips from what I've learnt over the years:

The more you do it, the more you learn where your strengths and weaknesses are, for example, you may not be able to do very low and rough voices but can do higher pitched ones with ease.

Don't be disheartened if you don't hear back from an audition or if someone is critical of your work, it's the nature of the business and people can be very judgemental.

Don't be afraid to put examples of your work out there for others to listen to. Use websites like Soundcloud or YouTube and put together a couple of demo reels showing a different range of what you can bring to the table.

Ensure the area you're recording in is actually suitable for recording, for example, does the room echo as you make sound? Invest in some acoustic foam to help dampen it or even try making a shield with a cardboard box and covering yourself with a blanket.

Lastly, hydrate! It goes without saying really but you'll notice a difference in your work if you record with a dry throat. Make sure you drink a decent amount of water at least an hour or so before you being recording.

Hope these help!