Teenagers are challenging under any circumstance -- especially when you try to talk with them. Parenting teenage foster children brings an additional set of challenges. The most critical step you can take to communicate with your teenage foster child is to build a foundation of trust. Easier said than done and it's not done in a day.
To start building a foundation of trust between you and your teenage foster child, start by really learning who your child is -- friends, favorite music, TV shows, colors, and foods. You can do this through observation and asking questions. Asking shows that you're interested in your teenager's life. However, teenagers (foster or not) can be notoriously surly about sharing their world with an adult. So make sure to take notice of what your foster teenager watches, listens to, talks about, wears -- anything that will give you information. Once you have an idea of what your foster teenager might like, give a small gift that will resonate with your foster teenager. Everyone likes knowing people really see who they are, so this is a good first step to building a foundation for your relationship.
Another step to take is to actively reach out to your foster teenager. You don't want to control the time and the place, but instead make sure your foster teenager knows you are available at any time. One method you can use is to give your foster teen a "coupon book" with each page a coupon for a talk. You can create specific coupons on specific topics, or just keep them general. Don't assume your foster teen will know you're open to talk, especially about difficult topics. It's your job as the parent to let your foster teen know you want to connect and are open to talk -- about anything.