Don't be afraid to say "i don't know" inresponse to student questions.When I began teaching I thought it would be a sign of weakness or lack of knowledge but students will respect you much more for being honest and learning together.

I totally agree. In reality you will know more than you realize...it may just be a temporary lapse in recollection. Students can relate to you more if you are honest. Always tell them you will find out or you can incorporate those instances into group learning or discussion in your class. This puts the students at ease because they won't feel like they are the only ones who "don't know" the answers.