Shoreditch and Dalston are the coolest neighborhoods — creative, affordable compared to central London, excellent food scene. Marylebone is quiet, upscale, and well-located between the West End and Notting Hill. Southwark (South Bank) puts you at Tate Modern, Borough Market, and the Globe Theatre — great mid-range options. Bloomsbury suits those focused on the British Museum.
Westminster and Mayfair are convenient but expensive and lacking in neighborhood character. For budget stays, look at Paddington, Earl's Court, or Bethnal Green — all well-connected by Tube. Boutique hotels in Notting Hill and Chelsea have the most character. Book early for peak summer — London fills completely in July and August.