Best way to do it is to go to preferences (may be options under the "tools" section on a PC, I'm on a Mac currently), go to "advanced" if applicable, and go to "shortcuts, and enable "single-key shortcuts". That will let you switch to the next tab by pressing "2", and the previous tab by pressing "1".
Also, there is no way to set it so that it always opens up a new tab in the background, as far as I personally know (correct me if I'm wrong). However, when you right-click something you want to open, you can click "open in background tab", which will let you open it in a new tab without changing tabs. The keyboard shortcut for that is control+click.