When one is applying to a startup of less than 20 people, is it necessary to use a formal cover letter, or will a simple, polite email do? I dislike cover letters because they feel extremely artificial. In my CL template, I end up talking about how, in high school, I woke up at 5:00 am to practice for contest math tests (e.g. USAMO). It makes me sound impressive and hard-working to HR people, but as I'm 25 and that was in HS, this sort of detail is completely irrelevant to whether or not I can write code.
Also, is it a good idea to wear a suit for a startup interview, or is this over-the-top or absurd? I'm afraid that overdressing might make it appear like I don't know how to interview for startups or, worse yet, type-cast me as similar to the species of douchebag college kid that generally applies for I-banking positions.
If it's not necessary to use cover letters and wear suits for startups, the next question is: where does one draw the line? How does one determine in advance whether or not an interview necessitates a suit?
Take that out. It doesn't matter what sort of job you're applying for -- the words "high school" should never appear in the resume or cover letter of anyone who has a college degree.
As for the rest: Dress like the job you want to have, not like the job you're applying for. If I was applying for a management position at a bank (not that I can imagine why I'd ever do that, but hypothetically...) I'd still turn up for an interview wearing a t-shirt and jeans. If my apparel wasn't up to standard, that would be an indication that the job I was applying for wasn't actually a job I wanted -- and being not offered the job would simply save me the trouble of quitting after a few weeks.