Many mistakes are made when submissives first contact a Domme. The biggest mistake seems to be not following directions, which means this post may fall on deaf ears. However, I will make an attempt anyway.
When addressing Her, refer to Her by Her preferred title. This is not an act of submission, it is simply being polite. “Sweetie”, “Babe”, or “Honey” and the like are unacceptable and disrespectful.
Do not default to a D/s mindset and attitude before negotiations! This is annoying and wastes time at best, but also comes off as an effort to get free scene time, and can be harmful to your future session. At any rate, not a good way to make a first impression. W/we need you in a clear state of mind for negotiations, which you might not be if you've already switched into submissive mode. Negotiations are there to keep U/s both safe and to make sure you get the scene and treatment you desire. We are not mind readers, We don’t know what you want!
Do not attempt to negotiate Her prices. By doing so, you are telling Her that you feel She is worth less than She is. This is a grave insult. Unless She lists discounts, that She will barter, or any specials, do not ask for one! You knew what Her prices were when you contacted Her.
When you book a session, pay the deposit! I don’t care if you’ve been burned in the past, or if you have trust issues. Pay. The. Deposit.
Do not ask Her to break Her own rules! The rules are there for a reason. She needs to keep herself physically, mentally, and emotionally safe. Asking Her to do this conveys that you feel you are more important than She is. If you continually ask for things She doesn't do or for Her to break Her rules, there's a good chance She won't session with you. Guys who push for little things end up pushing for bigger things and don't have any respect.
Do not ask for freebies! This happens frequently with new and ignorant submissives. A freebie would be: additional and unnecessary phone conversation; chat; or pictures/selfies. If She is an established professional, She should not need to verify. Verification is already done if She is listed on any sort of site such as Clips4Sale or NiteFlirt.
Do NOT call her booking line unnecessarily! Anything that needs to be discussed can be talked out via email. Let Her determine if it warrants a phone call and let Her call you.
Do not ask Her to send you a selfie. I don’t care if you sent one first (which She didn't ask for), you miss Her, or you are excited about seeing Her. She may be busy, not in a position to take one, or otherwise preoccupied. We do have lives when We’re not in sessions, and asking Her to do this is asking for extra work for free. There’s a REASON W/we sell pictures!
Do not send her a private message on her Twitter or FetLife if you're looking to serve if she specifically states to email her. When you email Her, include all of the information She's asked for so She doesn't have to repeat Herself! Also, make sure your message has a point. If your email is simply stating "I've been looking for a woman like you." or "All those kinks are so hot!" this doesn't provide Her with any information and you may not get a reply.
Above all else, read and follow Her protocol! This shows that you've paid attention to the initial rules She's laid out, that you're willing to serve, and that you're good submissive material. I do hope this helps, and by all means, keep these tips in mind when messaging ME!