I'm going to Miami in late December and would love to get some recommendations on which restaurants I need to start making reservations to.
I generally frequent and love to explore local-feeling not too fancy joints.
Good question. I think, like most other places, it depends on a few factors; like number of people in a party, week night vs. weekend night, etc. Since you mentioned that you want to experience the more local side of things an advance reservation may only be necessary for a certain few places, you probably wouldn't have a hard time getting into most local spots, or would be fine with making a reservation the day before or the day of. That said, if you plan to do brunch somewhere I would go ahead and make a reservation ahead of time.
I can recommend some places for you to check out off the bat but if you want more restaurant recommendations based on where you're staying or based on other food interests, just let me know.
Be sure to check out Eating House Miami especially for brunch, Yardbird Southern Table & Bar anytime of day, Michael's Genuine Food & Drink, Macchialina for great italian food (short rib lasagna is killer; they also have a cool brunch), Drunken Dragon is new great Korean food and good drinks, Pubbelly or Pubbelly Sushi, The Dutch (probably need a reservation), The River Seafood & Oyster Bar, El Mago De Las Fritas (for an authentic cuban hamburger), Mignonette, grab a drink and some tacos at Wood Tavern, and lastly get your stone crab fix Joe's Stone Crab (definitely need a reservation). Hope this helps, have a good trip.
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Restaurant Michael Schwartz at the Raleigh Hotel is beyond amazing. Try the pumpkin side dish and don't forget to have one of their famous martinis!!!