You're the go-getters.  You've taken the initiative and built a personal brand on Twitter and on your blog.  You've participated in industry events.  You may have an internship with an agency or consultancy under your belt.  You've done everything right to enter the social workforce.  So you should be all set to go, right?

Pretty much.  But first, it's important to level set and prepare yourself, your online profile and presentation for the professional world.

Making the transition into the professional world

1. Let's be clear, you probably have very limited real-world brand experience.  Remember, until now you have by and large been an amateur.  This is the real world.
2. You are not hired for your personal brand.  Your personal brand is great, but it's not why you will be hired.  You will be hired based on the promise you show to (a) be trained and part of a team, and ultimately (b) generate revenue for your employer by (c) participating in real-world marketing.  This is the real-world.
3. You don't know everything.  And nobody expects you to.  The ability to think is important, but so is the ability to listen and work with a team.  Being a talking head on Twitter doesn't qualify you to build marketing strategies.  Leave the posturing at the door.  Only engage in future casting when asked.  And don't speak in absolutes (ex Twitter will be dead in 6 months) unless you're damned sure of it.
4. Re-examine your posts and tweets, and rethink everything you post moving forward.  Brand bashing will likely not be tolerated, wherever you end up.  The world is a smaller place than you realize.  Don't burn bridges by venting on a brand that could one day be a potential client or employer.  And once you're hired, make sure you know exactly what your employer's social policies are.  Don't push them.
5. Leave your personal brand ambitions at the door.  Up until the day you are hired, your goal was to build your personal brand.  Now you're goal is to drive business.  If you can make it coincide with your personal brand goals, great.  But from here forward, your primary goal in the office is to the drive the business of the office.
6. Learn to listen.  We all love the wonderful visionaries in this space.  But you don't work for them.  You work for your boss.  Bring the visionaries' lessons learned, but think twice before pushing back on your new employers take on things.  You just may find that there is a good reason why some talking heads talk, and many of those who do haven't yet shared.
7. Embrace process, embrace teamwork. Life is more complicated when there are other people to coordinate with.  This is how the sausage is made.
8. Embrace criticism.  You are going to make mistakes.  There is a good likelihood that you may well know more than people far your senior.  You may step on toes.  You may remain silent when you should have spoken up.  This isn't about being right.  It's about furthering your career.  So ask for feedback, and make a real effort to embrace this feedback.
9. Don't share.  It's counter-intuitive to much of the user social dynamic, but nobody makes money by giving away the farm.  Your client meetings, strategies, internal processes and brainstorming are all proprietary.  Don't share, and don't share your thoughts or feedback in public.
10. Stay young.  Your enthusiasm will be infectious.  It will breath renewed life and vigor into the team.  Don't forget your idealistic dreams.  Just don't shove them down everyone's throats.