1. Be honesty
Since this person is your friend and close friend, honesty is the best strategy. If you're dating someone other than your FWB, be honest with them. If they find out that you are secretly dating another adult friend without telling them, they will feel very sad and hurt. You have to be honest with them about your physical condition, including, of course, your emotional feelings. If you don't have emotional attachment to them, it's good, it's ideal. But if you start to have an emotional attachment to them, tell them before you feel stronger that you will be more attached to them than they are. In this case, the relationship often disintegrates and becomes very chaotic.
2. Carefully consider whether you are really ready
If you really plan to build this NSA relationship with a friend of yours, before you do, think carefully about whether you really think about it and whether you are really ready. Even if your previous friendship is stronger, you need to know that things will change when the relationship has sex. It may make you feel embarrassed or regret what you have done before. Be sure to discuss the pros and cons, and make sure it's good for both of you. Although this may be surprising, sex is not the most important thing in the world. In fact, I'm sure friendship trumps it.
3.Be mature
If your FWB terminates your current NSA relationship, or wants to establish a serious dating relationship with you, for whatever reason, as long as it is not what you want, you should not easily agree to his request. You have to make your own decisions, and the decisions you make should be from your perspective, and you should not be controlled or influenced by anyone else. Although your idea is not consistent with his, you should also do not hurt him when you refuse him. This is a mature performance.