Folks, please don't post answers like "I like __field" or "I like m__field". It's a very personal and subjective question without a single answers.
If you have any guidlines it's already a big win. Worse thing in dev team is a lack of common conventions.
It would be nice if would try to describe some benefits of given guideline.
For example:
prefixing fields with underscore can
improve auto-completion with
intellisense
