One for one, we'll say the next number (no jumping from 10 to 87!) and try to get to 100. The goal is 100 because we're incapable little shitheads and the three times i'd set up an attempt to get to 1000 we never made it. No back to back, when you commented the next number in line, you wait for someone else to say the next number, then it's your turn again. In case of a number being said twice, the next person chooses which one to continue except not their own previous number. Good luck!