Learn together. You don't have to be fluent in another language. Bilingual books, toys, and other products can teach you both. Also, try to connect your child with native speakers. Consider hiring a babysitter who speaks another language or look for a playgroup of moms and babies who speak the language you're interested in.
Be consistent. Use the "one parent, one language" rule. If you're fluent in another language, speak only that language with your child while your partner uses English. By age 2, she'll know which language to speak with which adult.
Take it one word at a time. Encourage your child to use the words she learns. Even if she doesn't retain much at this point, just hearing and speaking another language will give her a jump start on the ability to interpret and pronounce foreign sounds, which will make learning another language down the road easier.