So you want to edit H.264 media in Avid? This is how I like to deal with it.
I always like to transcode H.264 media into a DNxHD format, but I have noticed that it is faster (for some reason) to bring it in via AMA first then transcode rather than do a straight import and transcode. Also, this provides a way for you to bring in new media and take a look at it in case you want to only transcode certain takes/files.