Jaydles' answer provides some reasonable guidelines for most questions that would reasonably be considered "biology" questions. However, I recommend treating one specific subcategory a bit differently: questions seeking medical advice.
I hesitate to even bring this up because we haven't actually seen any of these yet, but if past sites on related topics are any indication, a few of them will crop up eventually... And when they do,
Please resist the urge to answer them. Topics such as the treatment of chemical dependency, withdrawal, poisoning, allergies and so on have very serious potential consequences, and those dealing with them should be strongly encouraged to seek out a medical professional. Remember, answers here will be found and read by many, many people beyond just the asker - putting potentially life-threatening advice out on the 'Net is not something we should encourage.