You can use a screen reader to quickly skim a page by just listening to link text. Link text that makes sense out of context is very useful, “read more” or “click here” not so much. Use the same text for the same link every time. “Contact us” shouldn’t change to “get in touch”.
Underlines are the accepted convention – everyone knows they mean that’s a link. Don’t use underlines for emphasis (bold works, right?). People will keep trying to click your emphasized text.
Opening links in a new window takes control away from your users. It disables the “back” button. It makes it hard to use for a lot of people – including the ones who have 30 browser tabs open. If you really need to open links open in a new window warn your users.