Ask HN: Trademarking advice. Do you do it for your startups?

Hi there Hackers!

I wanted to get some advice on trademarks. As a startup, you're always out to prove your concept by building your MVP on a random but available domain. My question is this, did you all register your trademarks?

Reason I am asking is that I've not thought about it yet although hear that its very important. Something I'd like to know is what is the best practise advice for doing it? Also if you build a website with global reach (pretty much all of them are these days), would you have to register it globally? Would a local approach work first as you grow or is that advised against?