Where to eat in Milan

Al Baco di Andrea Carola (via Marconi 1) +39.02.5412.1637 (closed Sunday)
A local Osteria focused on Milanese cuisine, with friendly friendly service, local artists on the walls, and, well, just generally happy-making.  Go with whatever the specials are, you won't be disappointed!

Acqua e Sale - la Paranza Imperiale (via Alserio 15) +39.02.668.5448
A neighbourhood-y seafood place, tucked away in the rapidly hipsterizing Isola. It's local, it's friendly, and it's very *very* good.

L'isola Del Tesoro (via Ludovico da Viadana 2) +39.02.58307003 (open daily)
Neighborhood restaurant focusing on Sardinian cuisine, alongside the usual Milanese stuff (like monster-huge veal milanese).  The ambiance may feel slightly tacky at first pass, but the food is extra-ordinarily good - as evidenced by the overwhelmingly "local" patronage.
Get anything, but pay attention to what the daily specials are, and be sure to order seafood :-)

Luini (via Santa Radegona 16) +39.02.86461917
Its a wee tiny bakery that makes panzerotti (think "pizza pockets").  They make two or three kinds each day, and they are - uniformly - extraordinarily good, as evidenced by the huge lines outside the bakery pretty much any time of the day.

Non Solo Lesso (via G. Broggi 13) +39.02.36533440 (open daily)
A little tiny restaurant off the beaten path which, ostensibly, specializes in Lesso (boiled meats with a bunch of sauces on the side, enough to feed a reasonably sized horse).  We've never actually had any there, but everything else is ridiculously good.  The pastas, the carnes, the dolce, the, well, everythings are worth getting.  Basically, one of those places where you get in, sit down, and just let the host (the owner. his wife, in the kitchen, is the chef.  Son/daughter might be bussing tables...) guide you.
The table wines are great, but if you're feeling like splurging, have him pick something for you - give him a price point, and, if you can speak any Italian, discuss it with him...

Osteria Del Treno (via San Gregorio 36) +39.02.6700479 (No lunch on the weekends)
A slow food restaurant, where they take the "slow food" moniker seriously.  There is other stuff on the menu, but focus on the "slow food" labeled items - thats when you really understand what the movement is all about.  For example, they have a couple of salumi and formaggi plates that come from different parts of Italy, which are that much better than the versions you've had in the past.
Also, another place to discuss the wine with your host - they have an excellent selection, and they are more than happy to go into the pros/cons with you :-)

Pasticceria Marchesi (via Santa Maria alla Porta 11) +39.02.876730
Brioche. The best. Bar none. Go get some.

Pasticceria Martesana (via Cardinale Cagliero 4) +39.02.66986634
Brioche. The best. Bar none. Go get some.
(yeah, yeah. so is Marchesi. whatever)

Ratana (via Gaetano di Castillia 28) +39.02.8712.8855

Another slow food restaurant where they take the moniker seriously.  And, even more excellent, the celebrity chef is actually in the mix, always around and doing stuff.  The "go-to" dish is the risotto, which shows up in a slightly unappetizing form - brown osso-buco overflowing into saffron-gold risotto. But, one bite in, and you realize that this, *this*, is what risotto is supposed to be about (and the bone-marrow scooped into it just gilds the lily, and the lily is the better for it!)
Oh, everything else is just about as awesome - be sure to, as always, try and check out the daily specials.  e.g. the last time we were here, there were artichokes stuffed w/ anchovy paste (don't knock it till you've tried it!!!)

Trattoria da Pino (via Cerva 14) +39.02.76000532 (closed Sunday)
Go here for lunch - its pretty much a local/working-person's place, and the food is the perfect working-lunch - hearty, home-cooking, and admittedly somewhat heavy :-)