Communication is the single most important aspect in BDSM. I don't care if you're only into spankings by strangers or you're in a 24/7 Master/slave relationship. Nothing in BDSM should ever happen without plenty of communication first. Both sub and D should express their wishes.
The philosophy that you need to tell your partner everything isn't just hype. This isn't just about building a strong relationship or finding the love of your life (although both are certainly byproducts of good communication). Speaking up and sharing details about yourself, your likes, your dislikes, what you think, and your health impact your experience in BDSM.
If you're thinking that some details are simply too personal to share, remember that this person will most likely see you completely naked while you're drooling, sweating, writhing, and screaming. How much more personal can you get than that?
Both sides, top and bottom, Dominant and submissive, must be able to communicate their needs to one another. This lets you know if you're compatible. A sadist needs to know if the other person is a masochist. Before you tie someone up with rope, you should know if your partner has poor circulation or any type of anxiety when they can't move freely.
Sometimes the result of this communication is that you learn you don't want to play with that person. Sometimes the result is that you decide to do other activities together. BDSM is not a one-sided event. Two (or more) people are involved and every one should have their needs met, but no one can magically know what you need and what you want.
Put aside your concern about hurting your partner's feelings. As long as you treat the other with respect while you tell them what worked or didn't, a mature person will be able to handle it. The only way for both people to enjoy what's happening is to know what gets you off and, when something new is tried, what doesn't.
There are just some things people don't like. Me? I don't like rocky road ice cream (I know, some of you are gasping in shock). So when it's time to pick a flavor, I tell people. If not, I might get handed a cone of rocky road and be miserable. That's a simplified comparison, but if you've ever been offered ice cream and then found out it wasn't a flavor you like, you know the disappointment.
I don't like golden showers or scat play. Body fluids gross me out. So, before I engage in BDSM activities with a new partner, I tell them. If I don't make it clear that I don't like that kind of play, I might be in for a big surprise at some point and not find it sexy, erotic, or satisfying. Who wants kinky sex or BDSM play that's unsatisfying? What would be the point? Yet, that's what you get when you don't tell someone about your hard limits.
The good thing about communication in BDSM, especially when you set limits, is that you can always go back later and change your mind. If you're consistently communicating with your partner, you can tell them that you've given a previous hard limit, say ball gags, further thought, and you would like to try it. Simply because you've set a limit at one point doesn't mean you can't change your mind about it later. You simply have to communicate with your partner about it.
What does communication get you other than fun and kinky BDSM play? It builds trust and intimacy between you and your partner. When you're talking to one another in a meaningful way about your wants, your needs, your desires, what worked, what didn’t work, and your boundaries, you learn more about each other than you ever thought possible.
Baring your soul to another human being is empowering and uplifting. It brings you closer to that person. Knowing that they are communicating in the same way and sharing the smallest details of who they are brings you together. Not everyone who engages in BDSM play is looking for a love connection or a long term partnership, but the effects are the same whether you're communicating with your spouse, your significant other, or your favorite kinkster at the local club. You've built a strong bond between you that you might not experience with anyone else in your life.
For anyone new to the BDSM lifestyle, you might be surprised to know that bottoms and submissives have more control than you realize. A good Dominant or top will never violate a hard limit that has been communicated to them. They also won't engage in new activities until they've talked to their bottom or submissive about them, either.
Communicating boundaries and hard limits is one aspect of the control a submissive has; the other is the use of safe words. A safe word is a word or phrase that, when used, means all play should stop immediately. Some people use a color system. Green means keep going; yellow means slow down; and red means stop. Other people use words and phrases that don't make sense in the context of the scene. Pineapple, purple elephant, or rocky road ice cream, your safe word can be anything you want it to be. Make sure everyone in the scene knows it. If a submissive or bottom will be unable to verbally communicate during a scene, a hand signal of some sort should be in place.
Safe words help communicate a feeling of danger, unpleasant pain, or other feelings and sensations that mean the play or scene needs to immediately stop. Dominants and tops watch their play partners closely during a scene in order to avoid going too far or causing pain and distress. It can still happen. Using a safe word is not something to be ashamed of and no one should ever be made to feel bad for needing to use it. If a safe word is used repeatedly in scenes and other play, you need to talk to each other about what the underlying problem may be whether it's a physical pain, a fear, a worry, or a hard limit you didn't know about.
If consent is the key to BDSM in general, then communication is the essential first step. You cannot consent to anything without first talking about it in some way. Throughout a scene, kinky play, or a relationship, you must continue to communicate so that no one ever questions whether there's consent for an activity or not. If you don't like something, you have a responsibility to tell your partner. No one is a mind reader, and you will only get out of BDSM what you put into it. Set aside your fears of rejection and ridicule and openly discuss what you enjoy, what interests you, your fantasies, your desires, your needs, your wants, and yes, the things you really don't like, are afraid of, or consider outside of your boundaries. Only then can you experience the full beauty and eroticism of BDSM.