This is one of the most important suggestions. It is vital to establish your target language as the "normal" and most comfortable way of communicating with your child.
It is VERY difficult to switch to the target language once your child feels comfortable speaking to you in another language.
If you start speaking the target language with your newborn or young baby, you can progress in the language along with your child. You don't have to know everything at once.
Some Suggestions on How to Successfully Raise Children in Your Non-Native Langauge
Set Language Boundaries/Rules
Decide on your language boundaries and stick to them.
A boundary can be a person, a routine, a place, a situation, or even an activity.
You can have boundaries within boundaries. For example, if one of your boundaries is to always speak the target language within the walls of your home, you might also have another rule within that boundary that makes certain exceptions for guests.
Make sure that your children understand your family's boundaries.
Push the Target Language
During the younger years, it is important to get as much exposure to the target language as possible.
Once a child is around 5-8 years old, the community language will have a huge influence on their language choice, so make sure that they have a good grounding in the target language to compensate for other language influences.
Find a friend who is a native speaker of your children's target language.
If possible, set up a play group with other children who speak the target langauge
Acquire books, videos, music, audio books and games in the target language
Find computer programs and apps that help teach the target language.
Set yourself up for Success
Celebrate your unique situation. Help your children to feel proud of the target language and culture that they are acquiring.
Decide ahead of time what your language goals are. Be realistic.
Don't compare yourself to native speakers.
Understand that any language you give your children is better than no language.
Understand the many benefits of bilingualism and pat yourself on the back for exposing your child(ren) to a second language.