The best communication rules should be applied, regardless of whether you're part of a stepfamily or an original, nuclear family. Make sure you're really listening to what the other is saying, not just waiting for your turn to talk. Tell the truth, speak respectfully (especially when you disagree), and don't let arguments escalate into attacks. Also, take care with the type of language you use. If you want your family members to share with you, you should share with them. Tell family members about your thoughts and about your day. In addition, remember that communication is more than just talking; family members should spend time participating in activities together, laughing together, and planning specific times for the family to talk (e.g., family dinners).
When you're talking to your teen (step or biological), use all the approaches above, but also remember that conversation is more effective than a lecture, and don't back your teen into a corner with accusations.
When you're trying to communicate while building a new stepfamily relationship, you do have additional challenges. First, you always want to communicate your genuine affection for your stepchild, along with your respect. However, as a stepparent, you need to be part of the parenting with the original parent and you have to communicate your expectations of your stepchild's behavior clearly. Furthermore, one of the best ways you can model good communication to your stepchildren is to maintain good communication with your former spouse and certainly with your biological children. Your stepchildren will also be watching how you and your new spouse (their parent) communicate with each other. So if you two communicate well and resolve conflict in a healthy, positive manner, your stepchildren will feel more comfortable communicating openly with you.