Just in case you are thinking of speaking a language that is not your mother tongue to your child in order to help her/him become bilingual, DO NOT BE AFRAID. There was a lot of so called expert advice out there 10 to 15 years ago about how if your language skills were imperfect you'd pass those imperfections on to your child.
Well guess what, we're all imperfect in our native tongue as well! And so what if your accent is not "native"! There are so many different dialects and accents, and you are not the only person your child will hear speaking the target language. Make sure you have CDs, DVDs and ideally other humans around to speak the target language with your child and you'll be fine. Don't hesitate just because you aren't sure exactly how you are going to do everything -- you'll figure it out as you go along. If you want to do it, then BY ALL MEANS DO IT.