concerns on 3 somes!

1.what are some rules that are most reasonable to have. 2.who is best when it comes down to choosing the 3rd party when its with the father of ur kids! 3.what is some safe sex tips i should know that i might not already know. 4.and last but not least what is some things you could do to keep it interesting but not nasty! (i am considering trying it to make my man happy but very uncomfortable with it so please no harsh or judgemental comments if u disagree with my post please ignore and move on!!) ty!