Message Posting Advice

I am setting up our forum for people in our industry to network with one another and this is my first time working with a forum like this.  I am just looking for a little advice.  Generally speaking, should I allow users to edit and delete posts or should I limit them to creating new posts only?

Other than moving and renaming the database is there anything else I could/should do to try to protect our forum as much as possible from spammers?

Thanks!