Premier Inn at Albert Dock reasonably priced and in a great place. The Adelphi used to be The Savoy of the North, now avoid, whatever the deal.
If you stay at Premier, several nice breakfast stops - less 'pre-prepared' than Premier - actually on the dock.
Hanover Street Social and Salt House Tapas both great restaurants.
Tate Liverpool, Walker Art Gallery, Slavery Museum, both Cathedrals and Gormley at Crosby all unmissable.
Do the hop-on-hop-off bus tour, you'll see all the interesting bits.
Try The Baltic Fleet for a beer, it's lovely - The Philharmonic and Ye Cracke should also not be missed.
If you can find David Olusoga's A House Through Time - the Liverpool one - from BBC2 before you go, it gives context to the city, if you're interested in history.
Enjoy!