My husband and I used Natural Family planning to avoid, if you aren't using birth control this could be an option for you (we don't believe in bc). Basically you are looking for your CM to be drying up and you want to wait 3-4 days after your peak cervical mucus. This is most effective when you are also temping. Its called the sympto-thermal method
Just fyi - it didn't really work for us, we got married in July and because of the time change on our honeymoon I ovulated a little early and my husband has super sperm so we got pregnant and I am now 11 weeks. I just lurk over hear when my morning sickness is really bad so I really appreciate how blessed I amGood Luck!