This is a lot depending on what you want to achieve. A podcaster I follow uses twitter to organise with the people he meets around Germany. Others promote their newest content, their firms launched products, etc. I’ll just leave out talking about puppies or that you just had breakfast, because these you should do rarely, if you’re not breeding dogs or a dedicated food blogger. Your bio(graphy) is also important, so potential followers get a quick overview, what they’re going to read when they follow you. I’ll just use my current as an example:
PhotoDesignCode-Junkie, currently at the Nordic Multimedia Academy. Free for shootings and projects, speak to me in: EN/DE/DA. Follow me for more insights.
I consider it short, summarising my interests, revealing my current occupation, that I’m open for work, trilingual and inviting to follow me.
Try to connect with people you know in real life, people from the same area or field of interest. This will give you opportunities to jump into conversations, help or just get interesting updates. As this is a medium that leans so close against the pulse of the net as no other, being there when something happens or at least on a daily basis, you should make routine out of checking your account, mentions and retweets on a daily basis.