How do I decline sex?

Practice! It's going to sound stupid. But, say "no" until it isn't a word anymore.

It's your body. You owe no one sex. No one owes you sex. Giving some one sex is not a favor to them and telling them no is not a detriment to them. And if they tell you that it is then they're lying and manipulating you. There is no difference in saying "No, I don't want a soda.", "No, I don't want a smoke.", and "No, I don't want to have sex with you."
br/> Too many people make sex and rejection for sex a personal thing when in reality it has more to do with the person doing the rejecting than the person who is getting rejected. Be courteous and kind but it's more important to be firm and know what you want.

I agree with Swifting. Learning to say no can be difficult, but it's not impossible. It is important for yourself to practice and to say no. It is your body and your choice. Nobody should be using you as a toy. It is okay for you to say no, that's your right. If they have respect for you, they'll respect that you said no. If they don't respect that you said no, then they're not the right person for you at all. Don't let anyone do anything that you don't want them to.

When you are asked, take an honest look at yourself first if you really want it or think what's the consequences in the future if you will do it. We don't like regrets at the end. so if you have doubts when a guy ask you, then make an excuse, say' i have something important to do' or walk away. Think of yourself first. It's better to maintain your self respect than always question your self-worth after doing such.

You're a strong woman, you can make your own choices. When they start to pressure you into it, tell them no. Remember that you are an independent woman. You are the only one who controls your body, absolutely nobody else does and nobody should ever force you into having sex. No matter what other people try to tell you, there's NEVER a situation where it's okay to make you do that. Keep telling yourself this and build up your confidence, maybe find someone good who won't do that to you so you get a healthy source of happiness? Just a thought, good luck! :)

Well start by keeping your legs and mouth closed when they try to stick stuff in it.