Then you need to be aware of the policies.
Especially if you are going to be serving in Iraq or Afghanistan.
I have yet to pin down the exact location of the complete military blogging policies for deployed servicemembers, so if you know where I can find it to share with others, please pass it along. In the interim, here are some select phrases from the blogging policy adopted by MNF-I for Iraq, signed by LTG Vines in April 2005:
6-b: Personal web sites and web logs. Personal web sites and web logs produced in a personal capacity and not in connection with official duties need not be cleared in advance. However, it is the responsibility of MNC-I personnel to ensure that any personal web sites and web logs do not contain prohibited information defined by this policy. MNC-I personnel who have any questions regarding prohibited information may submit the information to their servicing S2/G2/C2 for classification questions or to their PAO for other questions. (Emphasis added)
More on milblogging in combat to come.