Twitter and social media is a big part of this job
Up your twitter game. They are looking for you to put your money where your mouth is.
This is what I'm thinking, and I've been forcing myself to be more active on twitter in posting. But I don't use my twitter profile to build an audience and most of my friends aren't on twitter. So I have 7 followers, and 5 of them are spam.
I think the bigger reason they are following you is to make sure you aren't posting stupid or offensive tweets, similar to how employers look at people's Facebook pages.
When I saw they were following me I did a mental rundown of my recent tweets to make sure I didn't say anything that made me seem like a giant douchebag.
As for your second question, a phone call is always the safer, and best, way to follow-up; it shows that you care more than an email or tweet would.
Hmm... Good point. But this is always the hardest part for me. What the hell do I say in the follow up? "Hi, I'm msteelers and I applied for this job. So... what's up?"
Hi, this is Ms. Teelers! I'm calling to follow up on an interview for the position of XXX with your firm, and would like to know the status of my application. I am excited for the potential your firm offers, and feel I'm a really good fit for the position.
They're likely to say something about someone being on vacation, or in the review process, or something like that.
Then you can ask : Would it be alright if I follow up on this at a later date? When would you suggest I check back, assuming I have not been contacted?
It's also fair to bring up the twitter follow, and be honest with them regarding that twitter account - set their expectation so they don't go "Dudez not no twit' skillz, yo" because they've decided to follow you at a social rather than professional level. If you feel you need to sell yourself, I'd suggest (long before calling) that you establish another Twitter presence for you to upsell.