I am an entrepreneur who does not like to be in the limelight. Am not a big tweeter or public figure. How can I still build my cred?
Having a great "personal brand" with loads of Twitter followers and a roster of conference speaking appearances pales in comparison to having legitimate, close connections to people who trust you and will vouch for you in any situation. Who are those people in your life? Who do they know whom you want to know? Ask for some introductions.
Frankly, a lot of social media and personal brand consultants are full of crap when they tell you to promote-promote-promote at all costs. When you're out giving keynote after keynote after keynote, you aren't building your product. Worse, it can also result in a startup brand that can't stand alone without its CEO, and for the long-term health of the company, you definitely don't want that.
Something you're going to want to consider is that while you don't like to be in the limelight, you may need to use some "limelight" tactics to build your company's reputation. I've seen a lot of successful cases in which a reserved or introverted entrepreneur makes sure that he/she has a reputable senior exec at the company -- maybe a CMO or marketing VP -- to be more "out there." You don't have to promote yourself, but somebody has to be promoting what you do. A respected advisor to your company can do this too in some cases.