As a start up entrepreneur there are many decisions that you need to take everyday. And if even 50% go correct, chances are that you will rise above the other umpteen competitors and create a brand of your own. Robert Scoble of the Scobelizer has a great post and follow up comments going here: http://scobleizer.com/2009/11/13/the-worst-things-startups-do/.
Some points that he mentions are a bit over the top like this one

11. Startups pick old technology because it’s familiar. You’re a startup, you should be picking the best of breed for everything you do. If you are using Microsoft Office “just because” then you are making a mistake. Have you considered Jive, SocialText, Zoho, Google Docs and Spreadsheets and Wave before making your choices? Have you really looked at ways to make your small company more productive? Or you just going with the same stuff your dad’s company used?

The other ones are more reasonable and offer some great insights into what you should NOT do as a start up.