When to Visit: London is pretty great year round! My personal favourite is the Summer months between about June to September, because it's warmest and there's so much on. However Spring and Autumn are beautiful for cherry blossom and Autumn foliage respectively. Christmas is also a magical time, when the city gets transformed! The only time I wouldn't recommend is January to March, when it's coldest and there's less to do.
Where to Stay: London has so many great neighbourhoods, you're spoilt for choice. Stay central (Leicester Square, Covent Garden etc) to be in the heart of the action, however these hotels will be most expensive. If you want to be somewhere happening with good nightlife, head East to Shoreditch. There's plenty of good hotels North in King's Cross and Paddington, or stay West for a quieter, more residential feel. See my full hotel review guide here.
Getting Around: London is best explored by public transport! The tube is (fairly) clean, fast, reliable (ish), and easy to use. It's also usually faster than getting a cab, and far cheaper. Buses can also be a fun way to explore the city, if you don't mind a bit of traffic. And most of Central London is easily walkable. Download the app Citymapper to easily find your way around the city.
Safety: I've never been mugged or pickpocketed in London, but it does happen. Keep your valuables safe, avoid having your phone in your pocket unless it zips, and watch out for thieves on bikes. Like every big city, you have to be vigilant!
London Top 5: Explore Soho and Shoreditch, galley hop in Kensington, shop on Oxford Street, Regent Street, and Covent Garden, dine at Fatt Pundit, drink at Cahoots and The Dickens Inn. Enjoy!