We have a fantastic public transport system in London but we have plenty of rules that make a visitor stand out when they don't know. Stand on the right on the tube escalator is one you soon get told as the left-hand side is for people walking up or down. This also means your luggage should be on the right and not block those who need to go past.
Speaking of escalators, don't get to the top and then stop as everyone behind you needs to get off the moving steps too. It sounds so obvious, but many people get to the top and then stop right in the way while they consider where they need to go next. Take a few steps away from the escalator and wait by the wall for friends or to read signs. It's much safer for all.
When travelling on the tube to or from Heathrow Airport, do not leave your suitcases in a doorway and then go and sit down. Yes, you may well have a long ride but your luggage is your responsibility. There are spaces on the Piccadilly Line trains for luggage to the side of the doorways and you can either perch against the padded wall-seat here or wait until the seat at the end of the carriage, next to your luggage, becomes free.
If you can, avoid traveling at peak times on the tube as it's busy and full of Londoners trying to get to and from work. It's cheaper to travel on the tube after 9.30am so wait for the morning rush hour to die down and then start your day. Explore near where you're staying too.
These London Underground Tips should also help.
2. Pavement Advice
You would think walking along the pavement (sidewalk) wouldn't need much advice but Londoners sure had a lot to say about this. The biggest gripes were people who stop in the entrance/exit of shops and museums to wait for their group. Please don't do this. That small space is for everyone and blocking the way is never going to win you any friends.
Consider the width of the pavement and if it's narrow don't walk in a line of 3 or 4 or more as no-one can pass. I'd generally say, keep children on the inside and don't walk more than two abreast on central London pavements. If you're a larger group, then someone has got to go behind or in front. Even on the wide pavements of busy streets such as Oxford Street it is better to not spread out.
Blocking the pavement and then walking slowly also irritates Londoners. We live in a city and therefore have a somewhat faster pace of life compared to country folk. We also get short lunch breaks and have long commutes to and from home so often are just 'head down' and focused on getting from A to B as quickly as possible.
When you want to cross the road, remember we drive on the left but there are many one-way streets in central London so have a look on the ground to see which way to look for traffic as it is often written by the kerb. Try to use pedestrian crossings, if possible. See Road Safety for Pedestrians for more advice.
There are a lot of chain restaurants, cafes and coffee shops in London. We're in a major world city so that's no surprise but that doesn't mean you have to frequent them all as 'you know what you're getting'. Starbucks caused public outrage in 2012 for not paying their full taxes and when they arrived here in the late 1990s they seemed to make a point of opening near independent coffee shops and putting them out of business. I'm a tea drinker not a coffee drinker yet I met a tea consultant who gave them lots of advice on how to improve their tea but they decided to focus on profit and not the product they sell customers. Totally a personal opinion but I don't go to Starbucks.
If you're out in town late in the evening, maybe after going to a nightclub, don't buy a hot dog or burger from the carts that are wheeled out at night. There have been many exposés about the poor hygiene standards of these temporary stands. When you feel unwell the next day don't say I didn't warn you.
Another chain establishment that has been the focus of exposés for poor hygiene standards, and the high prices should probably also be noted, is Angus Steakhouse. There are many better places to enjoy steak in London.
4. Personal Security
You have to look after your personal possessions in a big city like London so never leave your handbag open or your wallet in your back pocket. You need to be vigilant at all times and beware of pickpockets as no-one wants to lose their valuables and sometimes irreplaceable items. I have found my Scottevest Chloe Hoodie a lifesaver for zipping up valuables safely in inside hidden pockets. I have a pocket for my phone, camera, travelcard, and money with many spare pockets each day - and the hoodie doesn't look bulky with all that inside. A handbag that doesn't zip up sadly invites an opportunist thief to dip their hand in so ensure your bag does zip up fully. Zips delay a thief so use them.
Never, I repeat never think it's a good idea to swim in the River Thames. However inviting it may look on a hot day (we have a few of those in the summer) never get in the water. In central London, the Thames is busy with boats traveling in both directions all day long and the water is much deeper than you first think. The river is tidal which means it can be even deeper at times of the day and the tide comes in very quickly. A lot has been done to make the river clean, and many varieties of fish have been seen in the Thames, but this still does not mean it is clean enough for people to swim in. Even if you pop down onto the foreshore for a spot of mudlarking make sure you wash your hands thoroughly as soon as possible.
5. More Things to Never do in London
Don't queue jump. Yes, British people are known for liking to queue but while we have got a bit more flexible on this we still are horrified when we see someone walk straight to the front of line. Think about it, we've waited patiently and then someone thinks their time is more important than everyone else in the line and tries to butt in. It will not endear you to the locals I can assure you.
Don't think Tower Bridge is London Bridge. Tower Bridge is the most attractive bridge in central London, the one that opens, the one you can visit. London Bridge is the next one along and is nothing to look at. The current London Bridge was build in the 1970s although there has been a river crossing here since Roman times. The version of London Bridge before this one was bought and rebuilt in Lake Havasu City, Arizona.