1.) Do I need an oyster card or can I just tap my card?- You can just tap your contactless card/phone, obviously if you have an oyster card use that but it's not mandatory and many people just use their bank card
2.) Do I tap in and out?- Yes tap to get through and tap out at the other end, make sure you use the same card :)
3.) I've got an overview of how to do it but I'm worried it won't make sense. Is it really easy? Are there big obvious signs?- There's big signs directing you to the relevant platform and maps of the lines. Paddington is very well signposted
4.) Is Paddington tube station the same place as the train station or do I need to walk between?- Yes, Paddington train station and tube station are the same place. You will come out of the underground into the main train station
5.) Anything I need to be careful not to do? Like make sure I'm traveling in the right direction etc?!
- Don't stand on the left (Stand on the right, walk on the left, people will walk into to you if you're standing on the left)
-Don't be one of those people who gets to the tube barrier THEN decides to get their card out, have it ready before you approach the barrier, even if you need to stand to one side to make sure you have everything
-Likewise don't then stop on the other side of the exit gates to put said card away. Step to one side otherwise people will run you down
-If you're not 100% sure where to go listen to the announcements, if you go the wrong way just go one stop in the wrong direction, change platforms and go back :)
-On the platforms they are usually pretty well signposted if you need to change lines
-Download Citymapper, it'll plan your route, tell you of any changes and will also tell you where the tube will stop so you're right by the doors)
-Don't panic if you miss a train. If you're going at peak times there will most likely be another train in a few minutes
-If travelling via Kings Cross and you need the northern line make sure you get the right branch (For example if you get on say Tottenham Court Road, you'll need to travel north to Euston then change there for the Bank branch to Kings Cross)
-TFL have a journey planning tool on their website, put start and end destination and it'll tell you the best route
Finally, don't speak to other people on the tube (Fine if you're super lost and need directions but don't try and strike up a conversation on the tube). It's a golden rule, don't speak on the tube unless you're with your own party 