The key is to only move on to the next level once both partner's feel full comfortable and have discovered what feels best for them and their partner. I recommend at least a couple days at each level for you and your partner to fully reap at least some great benefits. You need to learn how to cue in to your own body and what feels good, but you should also be paying attention to your partner. It can also be beneficial to practice sensate focus (or at least nondemand touch) every once and a while for a day or two throughout the course of your relationship.
Level 2: Nondemand Touching and Caressing Including Breasts
Check in with your partner regarding each other’s level of comfort with Level 1. Talk to each other. Did you learn anything new? What was it like to give feedback to your partner and tell them what your preferences were with how they touched you? What was it like to tune in to your partner’s body language and sense what they wanted? What was it like to have gentle touch without expecting intercourse? Once you have discussed your experience and both express comfort, you are ready for Level 2.
Level 2 of sensate focus includes more nondemand touching and caressing except now you may include breasts. Which areas of the breast are more sensitive than others? Do you find you are aroused? Do you find that you enjoy nondemand intimacy? Find out what you like and don’t like and help your partner to understand. The relationship has to be safe for this to be effective. Be open, honest and loving.
Possible Modifications (Bonus Points):
Don't talk to each other. Cue in to each other's body language to see what each partner enjoys.
Turn out the lights or close your eyes.
Engage other senses. Light a candle. Face each other. Wear perfume.
Focus on one body area each day.
Spend an hour giving each other massages
Tell your partner what you like in their touch.
Grab his/her hand and guide them instead of just telling them.