As a documentary photographer, I regularly cover events. My event coverage has ranged from major public events, such as the 2009 Presidential Inauguration, to corporate events and recently an event put on by the Hells Angels Motorcycle Club. The following is a list of critical tips for getting the images when there are no re-shoots.
This list covers three critical areas: preparation, sensitivity to client's needs and pacing yourself.
1. Always troubleshoot and reacquaint yourself with equipment with sufficient time to fix or replace. Whether you are an aspiring photographer or working professional, we all have our lulls away from shooting day in and day out. When you have a gig scheduled after you have been away from your equipment for some time, take a few minutes and check your gear. Give yourself enough time to replace worn out or missing gear. Once you are on the job site, it's too late. Remember, failure of one piece of critical gear can put an end to the gig.
With the advances of digital photography, any bum with a decent DSLR can hold them self out as a “working professional.” Long gone are the days of serious study of technique, form and exposure as fix-it-in-the-mix, low cost, “good enough” images massage their way through post-shoot computation as professionally passable. In high impact markets, such as Los Angeles and New York, this creates tremendous market confusion. So, how does the true professional rise above the muck to reach potential clients? 
One fine spring day, I plunked away at sprouting lupine and California poppies in a vast green field, when my bliss was interrupted by a voice from behind. “Slow lens!” this photog grunted, stomping toward me.