I haven't incorporated any of them, I see that as an unnecessary hassle.
I'm in England, and (as far as I'm aware) quarterly taxes aren't a thing here. Until this year the income was negligible enough not to bother paying taxes, but this year I've been keeping track of finances with ledger[2] and I intend to pay taxes as "self-employed" for the first time at the end of this tax year.
And to make sure I'm going in the right direction (not going to run out of money) I add up my net worth, split by category (bank account, peer-to-peer lending, stocks and shares, Bitcoin) at the start of every month and keep track of it in a big text file.
[1] currently focusing on SMS Privacy, read my Indie Hackers interview at https://www.indiehackers.com/businesses/sms-privacy