Hi Evildouble,
Kinda a general question to answer but I'll give it my best shot.
Boundaries should be set when you start a relationship and it's up to the couple to define them. For instance, if you began dating someone and they wanted to take you home and have sex, you could define a boundary that you do not sleep with people until x,y,x (your in love, you've been dating awhile, etc.).
There are people who want sex and not a relationship, so maybe their boundary is that they can sleep together but no serious relationship. See? It can be exactly opposite.
People have many boundaries that vary. Some people don't like to be hugged by friends or strangers and will say so.
The bottom line is that it is your body and you will know when it is right to go one step further. If it's uncomfortable you say so. And if that person doesn't understand or gets mad then that is their issue not yours.
I hope this helps, it's kinda a hard question to answer
Tranquility