Here's a discussion from some Marketo folks before that includes ideas that I have put into practice. And this Marketo University webinar includes a section about naming conventions as well. Hope they help!
We have our Marketing Activities organized by year. This way we can archive the previous years easily. But then we also have folders for scoring, data management, forms, etc.
As for naming, I prefer to have the date first and then the name and location. Ex: 2013.07.15 - Big Launch Webinar - (if event, I'd put locaiton here)
And another thing I find helpful when naming steps within a program is to number them... this way they're listed in the order you'll be activating them and it makes it easier to get a hold of... 1) Registration 2) Invite #1 3) Invite #2 4) Reminder 5) Follow-up etc.