Here’s my steps
Do your research and target the labels you are sending to, take time to make sure you listen to all the music they’ve put out
Send only your best couple of tracks and make sure each is a private link, preferably with using something like soundcloud pro to monitor the plays
Use an individual link for each person you send it too, with zero plays on each if you are using soundcloud
Be original! Smaller labels on your way up will either dismiss big samples because they won’t want to clear them
Make sure you use a personal email, NEVER a just send a link in an email, it will Get deleted straight away, try to give information about you and your recent success, keep it short but to the point.