Reddit reviews Lonely Planet London (City Guide)

Do yourself a favour. Invest $20 in one of these: https://www.amazon.co.uk/Lonely-Planet-London-Travel-Guide/dp/1786573520/ref=pd_lpo_sbs_14_t_1?_encoding=UTF8&psc=1&refRID=7TPSGSBWG2PTF3ZC96Y1

Also post in the stickied thread at the top of the subreddit, where you'll have a really helpful first post with lots of links to our wiki. You'll find a guidebook helpful too - something like Lonely Planet London and the Pocket edition for quick reference while you're out and about. You'll probably find most of your questions (how to get around, how to see the big sights, what to do/not do about tipping etc) are answered in there.