A bottom is the person in the scene that is receiving the kink or being led around by the Top (the giver of kink). With that out of the way, what are some things you can do (or have done) if you are going to be a better bottom in a scene?
Being an active bottom will not only help the Top out, but it will also help you have the best scene possible. Unfortunately some people think the bottom just shows up, receives kink, and their job is done.
Be active in the negotiations for the scene, ask questions, and be willing to share personal info if it can directly affect you or your part in the scene. Also discuss your experiences (good and bad) with that kink and what position(s) work best for you. Let them know if you have experience with subspace, how you acted in subspace, and should they continue the scene or end it. (Only continue the scene with someone you completely trust with your life, as you might not be able to communicate at this point)
Have your own toys. Some toys can not be sanitized, and should not be shared unless you are fluid bonded with that person. If you have a fave toy you want used in the scene, bring it, but make sure the Top knows how to use it properly/safely.
PRICK (Personal Responsibility, Informed, Consensual Kink) evolved from SSC and RACK. Prick is asking everyone in the scene to take personal responsibility for their kink. Meaning you understand the kink, what is going to happen when doing that kink, all safety aspects and the risks involved with that kink.
Ask the Top what they need from you in the scene, compatibility is just as important in a Top/bottom dynamic as it is in a Dom/sub dynamic.
Ask the Top what aftercare they need. Check in with your Top to make sure they are ok. Tops are not kink dispensers, they have feelings, might need aftercare, and need reassurance that they are not monsters for what they do to us. They also can drop (Top/Dom drop) which is just as serious as sub drop (and hardly ever talked about).
The scene is for the Top, just as much as it is for the bottom. Working together as a team with a common end goal is the best way to have a successful and pleasurable scene. Communication should keep going even after the scene ends (on a level you are comfortable with), after the aftercare is where you discuss the good and the bad in the scene. As a bottom, speak up if there was something you really enjoyed, or something you did not. You can use this info to help shape and better future scenes with that person, while helping you grow and push your personal limits in that kink.